



















































































































































































































































































































































































































































































COPYRIGHT DEPOSIT, 











I 



. 




J T 

r- 


























V i* 


. ** i 






























































• 









BIOLOGY 

FOR 

IGH SCHOOL 


BY 

ft 

W. M. SMALLWOOD 

n 

SYRACUSE UNIVERSITY 

IDA L. REVELEY 

WELLS COLLEGE 

GUY A. BAILEY 

GENESEO STATE NORMAL SCHOOL 




ALLYN and BACON 

BOSTON NEW YORK CHICAGO 


ATLANTA 


SAN FRANCISCO 



COPYRIGHT, 1920, BY 
W. M. SMALLWOOD, IDA L. REVELEY 
AND GUY A. BAILEY 



v SEP 29 ib^U 


Norinooh 

J. S. Cushing Co. — Berwick & Smith Co. 
Norwood, Mass., U.S.A. 

©CU576668 




Co 

©ur Sima fHatrr, Sgracuse fflnitersttg 

Cn i&ecogntttou of tfj£ Completion of 
jftftg gears of iSet&tce to lEtiucatton 























































































. 
























. 


























' 















' 1 t ^ 















































PREFACE 


Biology for High Schools was written to show the close 
relationship of the science of biology to human life. The 
treatment gives a broad survey of the life of plants and 
animals, including man. 

Specifically the book aims to do six things : 

(1) To teach the pupil to see accurately what he looks at 
and describe exactly what he sees. 

(2) To teach him to think clearly and to base his conclu¬ 
sions upon his facts. 

(3) To broaden his knowledge of his own body through 
the study of the structure and functions of other animals 
and of plants. 

(4) To show him by the adaptations of plants and ani¬ 
mals how he can adapt himself to the varying conditions 
of life. 

(5) To make him a good citizen through his knowledge 
of good food, good health, and good living conditions. 

(6) To teach him how biology has helped human progress 
and welfare. 

Biology for High Schools gives due attention to laboratory 
and notebook work. It makes the most of the pupil’s 
interest in recording personal discoveries about living things, 
and guides him by easy steps from simple pencil sketches to 
more elaborate pen drawings. 

A special feature of the book is the thorough treatment 
of the practical side of biology, with reference to the pre¬ 
vention of disease, particularly in its epidemic forms, through 
sanitation and right living. 

The last chapter is on Biology and Human Progress , and 


VI 


PREFACE 


treats such varied subjects as the new discoveries which 
have made for progress by improving human environment ; 
quarantine regulations for the protection of domestic fruits 
from foreign destructive insects; the functions of the United 
States Department of Agriculture; and the principles of 
variation and heredity as they affect both the cultivation 
of the soil and human life. 


May, 1920. 


W. M. S. 
I. L. R. 
G. A. B. 


ACKNOWLEDGMENT OF ILLUSTRATIONS 


Guy A. Bailey, Bird and Mammal Photographs (in nature). 
W. L. Bray, Syracuse University, 342, 347, 348. 

Fred Baker, 316. 

Hugh P. Baker, 322. 

S. S. Berry, 179. 

M. W. Blackman, New York State College of Forestry, 
4, 89, 90. 

W. E. Britton, Connecticut Agriculture Station, 25. 

W. Coe, Yale University, 161, 162. 

Conservation Commission, New York State, 327, 328, 329, 
335, 336. 

Cornell State College of Agriculture, 357, 434, 435, 436, 437. 
Hugh Findlay, 16, 200, 282. 

Fitzhenry-Guptill Co., Boston, 5. 

Earl Hallenbeck, 396, 397. 

C. W. Hargitt, 152. 

Illinois State Laboratory of Natural History, 340, 341. 

D. F. MacDougal, Desert Laboratory, Tucson, Ariz., 344. 

W. A. McKeever, 421, 422, 423. 

Dr. J. S. Marshall, Berkeley, Cal., 368, 369. 

S. 0. Mast, Goucher College, Baltimore, Md., 136. 

W. A. Murrill, 294, 295, 296. 

New York State Bureau of Health, 410, 411, 427. 

New York State Education Department, 128, 129, 130. 
Omaha Chamber of Commerce, 376, 377, 378. 

Dr. Edward Packard, Saranac Lake, N. Y., 424, 425. 

F. C. Pailmier, Albany, N. Y., 52, 53. 

Dr. C. Potter, Syracuse, N. Y., 371, 372, 383, 384, 385, 
386, 387, 429, 430. 

vii 


viii ACKNOWLEDGMENT OF ILLUSTRATIONS 

A. M. Reese, University of West Virginia, Morgantown, 
W. Va., 91, 92. 

A. G. Rutheven, University of Michigan, Ann Arbor, Mich., 

83, 84, 86, 88. 

G. B. Simpson, 170, 171, 172. 

B. G. Smith, Ypsilanti, Mich., 70. 

W. H. Snyder, Los Angeles, Cal., 93, 126, 127, 244, 343, 349, 
428. 

Crystal Thompson, Ann Arbor, Mich., 71. 

J. M. Thorburn & Co., New York City, 242. 

C. H. Townsend, New York Aquarium, 59, 60, 61. 

University of Minnesota, 205, 245, 269, 351, 352, 353, 354, 

355. 

United States Census 1910, 375. 

United States Department of Agriculture, 12, 13, 17, 33, 34, 
35, 36, 37, 38, 40, 41, 42, 45, 46, 47, 49, 59, 66, 67, 68, 
69, 90, 125, 144, 180, 181, 279. 

United States Department of the Interior, 254, 323, 324, 326, 
330, 331, 332, 333, 334, 350, 358, 359, 431, 432, 433, 438. 
Jerome Walker, Physiology, 400, 407, 408, 412. 

Anti-Saloon League, 419. 

Wisconsin University, 246, 247, 274, 275, 356. 


TABLE OF CONTENTS 


PART I 

ANIMAL BIOLOGY 

PAGE 

Introduction.1 

CHAPTER 

I. The Grasshopper, an Introduction to the Study of Insects . 17 

II. Important and Familiar Insects.32 

III. Crustaceans and Related Forms.60 

IV. Fishes.68 

V. Amphibians ..82 

VI. Reptiles.99 

VII. Birds ..107 

VIII. Mammals.125 

IX. The Simplest Animals — Protozoa.141 

X. The Simpler Metazoa.152 

XI. Coelenterates. Hydra-like Animals.160 

XII. The Starfish Family.169 

XIII. The Worm Group.175 

XIV. The Mollusks.185 

PART II 

PLANT BIOLOGY 

XV. The Life of Flowering Plants . . . . . 195 

XVI. The Seed and the Seedling.219 

XVII. The Fruit 233 

XVIII. The Root.247 

XIX. Stems.260 

i 


IX 



















X 


TABLE OF CONTENTS 


CHAPTER PAGE 

XX. The Leaf. .... 274 

XXI. Other Flowering Plants.295 

XXII. The Simplest Green Plants.304 

XXIII. Smallest Plants, Bacteria.309 

XXIV. Fungi — Plants That Lack Chlorophyll . . .320 

XXV. Mosses and Their Allies.328 

XXVI. Ferns and Their Allies.333 

XXVII. The Conifers (Gymnosperms) — Forests .... 341 

XXVIII. Peculiarities of Plant Life.366 

XXIX. Some General Plant Problems.380 

PART III 

HUMAN BIOLOGY 

XXX. Resemblances between Man and the Other Animals . 399 

XXXI. Digestive Organs and Food.404 

XXXII. Movement.432 

XXXIII. Respiration and Excretion.443 

XXXIV. The Nervous System of Man.466 

XXXV. The Biology of Disease.487 

XXXVI. Prevention of Disease.497 

XXXVII. Biology and Human Progress.521 

PART IV 

GENERAL BIOLOGY 

A Summary and Review.539 


Index . 


1 













LIST OF ILLUSTRATIONS 


FIGURE PAGE 

1. Squirrel, Showing Adaptation.1 

2. Human Hand, Showing Adaptation.2' 

3. Seeds Adapted for Wind Distribution.3 

4. Typical Animal Cell ..7 

5. Tissue ..8 

6. Female Grasshopper..19 

7. Diagram of Grasshopper.20 

8. Mouth Parts of Grasshopper ....... 21 

9. Jumping Leg of Grasshopper.22 

10. Wings of Grasshopper.23 

11. Grasshopper Nymphs.26 

12. Codling Moth Larva..26 

13. Worm in the Apple.27 

14. Codling Moth . 28 

15. Modern Spraying Outfit.30 

16. Scale Insects ..32 

17. Cicada.33 

18. May Beetle.34 

19. Eggs of Ladybug.35 

20. Monarch Butterfly.36 

21. Larva of Mourning Cloak Butterfly ...... 37 

22. Transformation of Pupa of Mourning Cloak Butterfly into Adult . 38 

23. Cecropia Moth ..39 

24. Redheaded Woodpecker.40 

25. Young Tobacco Worm.40 

26. Swallowtail Butterfly ..40 

27. Larvae of Leaf Miner.40 

28. Wingless Female of Tussock Moth.41 

29. Tent Caterpillars.42 

30. Cedar Waxwing.43 

31. Protective Coloration.44 

32. Yellow Swallowtail.45 

33. Honey-bee.45 

34. Queen Cells ..46 

35. Honey-bee Egg and Larvae.46 


xi 











Xll 

LIST OF ILLUSTRATIONS 


FIGURE 


PAGE 

36. 

Bee’s Sting ....... 

- . • 

. 47 

37. 

Honey-bees Clustering at Swarming Time . 

• • • 

. 48 

38. 

Capturing a Swarm. 


. 49 

39. 

Hind Leg of Honey-bee .... 


. 50 

40. 

Tongue of Honey-bee .... 


. 51 

41. 

Model Apiary. 


. 51 

42. 

Worker Honey-bee Laden with Pollen 


. 52 

43. 

Thalessa Laying Eggs .... 


. 52 

44. 

Tremex 


. 53 

45. 

Common House-fly 


. 54 

46. 

Culex and Anopheles. 


. 55 

47. 

Eggs and Larvae of Culex .... 


. 55 

48. 

Crayfish, Showing Eggs .... 


. 60 

49. 

Molted Exoskeleton of Lobster 


. 61 

50. 

Organs of Crayfish. 


. 62 

51. 

Crayfish, Showing How Eggs Are Carried . 


63 

52. 

Soft-shell Crab .... 


. 64 

53. 

Pill Bug. 


. 64 

54. 

Cyclops. 


. 65 

55. 

Daddy-long-legs. 


. 65 

56. 

A Common Spider ..... 


. 66 

57. 

Tropical Spider. 


. 66 

58. 

Thousand-legged Worm and Centipede 


. 66 

59. 

Perch . 


. 68 

60. 

Sunfish 


. 69 

61. 

Brook Trout. 


. 70 

62. 

External Parts of a Bass .... 


. 71 

63. 

Scales of Fishes . 


. 71 

64. 

Gill of a Fish ...... 


. 73 

65. 

Eggs of the Land-locked Salmon 


. 76 

66. 

Young Fish Just at Hatching Stage 


. 78 

67. 

Young Fish Seventeen Days after Hatching 


. 78 

68. 

Grayfish . . . ... 


. 79 

69. 

Whiting. 


. 80 

70. 

Some Common Land Salamanders 


. 82 

71. 

Leopard Frog. 


. 83 

72. 

Diagram to Show the Organs of the Frog- 


. 86 

73. 

Kidneys of the Frog .... 


. 87 

74. 

Central Nervous System of Frog 


. 88 

75. 

Frog Eggs .... . 


. 90 

76. 

Diagram Illustrating Fertilization in Frog Egg 


91 











LIST OF ILLUSTRATIONS xiii 

FIGURE PAGE 

77. Dividing Egg of Frog ... ... 91 

78. The Embryo Becoming a Tadpole . .... 92 

79. Tadpoles.93 

80. Different Stages in Life History of Toad.94 

81. Fossils.95 

82. Tree Frog.97 

83. Rattlesnake .. 99 

84. Common Snapping Turtle.100 

85. Head of Rattlesnake ..100 

86. Horned Toad.101 

87. Rattles of Rattlesnake. . 101 

88. Garter Snake.102 

89. Bull Snake with Hen’s Egg in Mouth ..... 103 

90. Bull Snake after Swallowing Egg ...... 103 

91. Alligator Nest .. 104 

92. Eight-foot Florida Alligator.105 

93. Poisonous Lizards. . 105 

94. Regions of a Bird.107 

95. Herring Gulls ..108 

96. Adult Screech Owl.109 

‘ 97. Birds’ Feet.110 

98. Skeleton of Duck .. 110 

99. Head of Young Eagle.Ill 

100. Loggerhead Shrike .112 

101. Robin ..113 

102. Young and Adult Chestnut-sided Warbler.114 

103. Eggs of Woodcock . 115 

104. Junco. 116 

105. Kingbird . .116 

106. Female Bobolink . 117 

107. Kingfisher ..117 

108. Young Crows in Nest Waiting for Food ..... 118 

109. Hairy Woodpecker Eating Suet.119 

110. Male and Female Cowbirds.120 

111. Woodcock on Nest.122 

112. Nest of the Yellow Warbler.123 

113. Skeleton of a Dog.125 

114. Coyote ..125 

115. Flying Squirrel . .126 

116. Brown Bat. .127 

117. Bat Hibernating. 127 













XIV LIST OF ILLUSTRATIONS 

FIGTXKE PAGE 

118. International Champion Draft Horse . . . . . 128 

119. Standard Breed of Trotting Horse ...... 129 

120. Deer Mouse . . ..129 

121. Holstein Cow and Calf.130 

122. Prize Hereford Bull.131 

123. Hampshire Sheep ......... 132 

124. Rambouillet Sheep.133 

125. Berkshire Pigs.134 

126. Camel.135 

127. Bison. . 136 

128. A Beaver Dam. . 136 

129. Poplar Trees Cut Down by Beavers ...... 137 

130. Beaver House.138 

131. Runways of Muskrats ........ 139 

132. Photomicrograph of Amoeba ....... 142 

133. Diagram of Amoeba. 143 

134. Fission of Amoeba.• 145 

135. Diagram of Paramecium.146 

136. Paramecium .......... 147 

137. Paramecium Stained to Show Nucleus ..... 147 

138. Paramecium Reproducing by Fission ..... 148 

139. Vorticella.148 

140. One of the Foraminifera ........ 149 

141. Some Flagellate Protozoa.149 

142. Gonium.152 

143. Volvox.153 

144. Bath Sponge.154 

145. Grantia, Showing Parts.155 

146. Sponge Development . . . - . . . . 157 

147. Sponge Spicules , 157 

148. Fresh-water Hydras . . .161 

149. Diagram of Body of Hydra. . 162 

150. Cross Section Body-wall of Hydra ...... 162 

151. Photomicrograph of Hydra, Showing Eggs .... 163 

152.. Photomicrograph of Colonial Hydroid ..... 164 

153. Hydroid Colony . . . . \ .. . . . 165 

154. Medusa Known as Pelagia . . . . . . 165 

155. Medusa of Hydroid . . ..165 

156. Pennaria Tiarella.166 

157. Somp Common Corals ........ 167 

158. Starfish.169 













LIST OF ILLUSTRATIONS XV 

FIGURE PAGE 

159. Diagram of Body of Starfish ....... 170 

160. Embryo of Starfish ..171 

161. Purple Sea-urchin.172 

162. Common Sea-cucumber . 173 

163. Planarian Worm ..175 

164. Trichinella. .... 176 

165. Common Tapeworm ..177 

166. Hair Worm in Body of Grasshopper.178 

167. Organs of the Earthworm.181 

168. Nervous System of Earthworm. 182 

169. Dero.183 

170. Clam, Showing Foot.185 

171. Left Shell of Clam.186 

172. Digestive Tube of Clam. 187 

173. Embryo of Clam.188 

174. Snail.189 

175. Our Common Pond Snail. . 189 

176. Tongue of Snail.190 

177. Snail Shells.190 

178. Soft-shelled Clam.191 

179. Octopus ..191 

180. Stages in Life History of Oyster.192 

181. Barnacles and Clams Growing on Oysters.193 

182. Flower of Nasturtium.. . 198 

183. Flower of Nasturtium with Petals Removed .... 199 

184. Pistil and Stamen of Nasturtium.199 

185. Flower of Lily.200 

186. Stamen of Lily . 200 

187. Staminate Flowers of Corn, the “Tassel” .... 203 

188. Pistillate Flowers of Corn ..204 

189. Violet Plant with Cleistogamous Flowers.205 

190. Disk Flower of Daisy.206 

191. Ray Flower of Daisy.206 

192. Flower and Fruit of Dandelion.207 

193. Flower of Salvia . ..209 

194. Salvia.210 

195. Pollen Grain Sprouted.210 

196. Pollen Grains Sprouting and Growing through Style . .211 

197. Pollen Tube, Enlarged.211 

198. Pollen Tube Entering Ovule in Act of Fertilization . . .212 

199. Umbel.213 








xvi LIST OF ILLUSTRATIONS 

FIG-UKE PAGE 

200. Compound Umbel of Wild Carrot.214 

201. Compound Umbel of Wild Parsnip.215 

202. Cyme of Chickweed.215 

203. Panicle.215 

204. Compound Cyme of Elder.215 

205. Spike.216 

206. Photograph of Plantain Spike.216 

207. Bean Seed, Showing Parts ....... 219 

208. Seeds of Bean and Pea ........ 220 

209. Germination of Bean.221 

210. Bean Seedlings.222 

211. Diagram of Grain of Corn . . . . . . . 224 

212. Unsprouted Grain of Corn ....... 224 

213. Plumule Ready to Break Out ....... 224 

214. Plumule Free, but Bent by Accident.225 

215. Plumule Unfolding.225 

216. Advanced Corn Seedling. 226 

217. Diagram of Fruit of Rose.'233 

218. Cross Section of Orange, a Berry ...... 234 

219. Vertical Section of Apple, a Pome ...... 235 

220. Cross Section of Apple.235 

221. Chestnut, a Dry Fruit.236 

222. Samara, the Winged Fruit of the Mapie.236 

223. Leaf, Flower, and Fruit of Witch-hazel.237 

224. Cross Section of Cucumber, a Pepo or Fleshy Fruit . . . 238 

225. Capsule of Violet.238 

226. Capsule of Poppy.238 

227. Dry Fruits.239 

228. Vertical Section of Peach, a Drupe.239 

229. Akene of Dandelion. 239 

230. Seed Dispersal of Milkweed.240 

231. Fruits Distributed by Animals.241 

232. Fig-wasp. 243 

233. Vertical Section of Caprifig.244 

234. Cross Section of Root with Root Hairs ..... 247 

235. Cross and Longitudinal Section of Root.248 

236. Longitudinal Section through Root and Root Cap . . . 248 

237. Germinating Wheat, Showing Root Hairs . . . . . 249 

238. Bit of Epidermis of Root with Root Hairs.249 

239. Fibrous Roots of the Buttercup. 251 

240. Fascicled Roots of Dahlia.251 










LIST OF ILLUSTRATIONS xvii 

FIGURE PAGE 

241. - Aerial Roots of Ivy.252 

242. Tap Roots of Radish.253 

243. Extent of Root System of Corn.253 

244. Root System of Alfalfa.254 

245. Root System of Rhubarb, a Medicinal Plant .... 255 

246. Effects of Inoculation on Garden Peas ..... 257 

247. Effect of Bacteria on the Growth of Red Clover in a Poor Soil . 258 

248. Stem of Indian Turnip 261 

249. Starch Grains, Highly Magnified.261 

250. Potato ..262 

251. Dandelion Plant.. 263 

252. Stem of Horse-chestnut.264 

253. Elms.265 

254. Wood of Spruce, Greatly Magnified.266 

255. Cross Section of Corn Stem.267 

256. Corn Stem . . . . . . . 268 

257. Cross Section of Dicotyledonous Stem.268 

258. Cleft Grafting.270 

259. Whip or Tongue Grafting.271 

260. Skeleton of Poplar Leaf.276 

261. Leaf of Elm.276 

262. Palmately Compound Leaf of Woodbine.277 

263. Bit of Epidermis of Leaf.283 

264. Cross Section of Bean Leaf ....... 285 

265. Leaves of Barberry . 288 

266. Peltate Leaf of Nasturtium ....... 288 

267. Twining Petiole of Clematis.289 

268. Indian Pipe ..290 

269. Leaves of Young Plants of Pokeweed.291 

270. Pea Plant.292 

271. Vertical Section of Cabbage.293 

272. Walnut Tree . 295 

273. Leaf of Oak.296 

274. Siliques of White Mustard.297 

275. Single Silique Split Open ........ 297 

276. Base of Rose Leaf ..298 

277. Stem of Rose 298 

278. Nodules Caused by Bacteria on Roots of Bean .... 299 

279. Peanut ....... ... 299 

280. Flower of Columbine.300 

281. Calla, a Flower with Spathe and Spadix.300 







xviii LIST OF ILLUSTRATIONS 

FIGURE 

282. Common Field Daisy ..... 



PAGE 

. 301 

283. 

Pleurococcus .... 






. 304 

284. 

Spirogyra. 






. 306 

285. 

Spirogyra Conjugating 






. 306 

286. 

Bacteria. 






. 309 

287. 

Beef Jelly. 






. 314 

288. 

Beef Jelly. 






. 314 

289. 

Correct Stoppers for Milk Bottles 






. 315 

290. 

Yeast Plants .... 






. 320 

291. 

Fermentation Tubes . 






. 321 

292. 

Bread Mold .... 






. 322 

293. 

Shaggy-mane Mushroom . 






. 323 

294. 

Oyster Mushroom 






. 324 

295. 

Common Field Puffball 






. 325 

296. 

Bit of Lichen .... 






. 325 

297. 

Lichens. . 






. 326 

298. 

Types of Moss .... 






. 328 

299. 

Diagram of Life History of Moss 






. 329 

300. 

Marchantia with Archegonia 






. 330 

301. 

Marchantia with Antheridia 






. 331 

302. 

A Common Liverwort 






. 331 

303. 

Forked Veins of Fern Leaf 






. 333 

304. 

Cross Section of Stem of Pteris . 






. 334 

305. 

Pteris, a Common Fern 






. 334 

306. 

Diagram of Life History of Fern 






. 335 

307. 

Sporangia of Fern 






. 335 

308. 

Equisetum .... 






. 336 

309. 

Sporophyll of Equisetum . 






. 337 

310. 

Equisetum ..... 






. 337 

311. 

Club Moss. 






. 338 

312. 

Equisetum, Sterile Stalk 






. 338 

313. 

Sporophyll of Club Moss . 






. 339 

314. 

Equisetum Spore 






. 339 

315. 

Cross Section Stem of Equisetum 






. 340 

316. 

Conifers ..... 






. 342 

317. 

Young Female Strobilus 






. 343 

318. 

Male Strobili .... 






. 343 

319. 

Mature Female Strobilus or Cone 






. 344 

320. 

Pollen Grain of Pine . 






. 344 

321. 

Other Cones .... 






. 345 

322. 

Virgin Forest of Mixed Hard Woods and Conifers 



. 347 










LIST OF ILLUSTRATIONS xix 

FIGHJEE PAGE 

323. What Deforesting Is Doing in the United States . . 349 

324. What Deforesting Did in China.350 

325. Diagram Showing How Logs Are Quarter-sawn . . 351 

326. Photograph of Sections of Wood.352 

327. Nursery Where Young Trees Are Started.353 

328. Young Plantation in the Adirondacks.354 

329. Young Plantation 16 Years after Planting ..... 355 

330. Forest Fire in Montana. 356 

331. The Result of a Hurricane and Fire in Idaho .... 357 

332. Castle Peak Fire Lookout . . . ..358 

333. Sign Containing Warning about Fires.359 

334. Poster Warning against Fire ....... 360 

335. Fire “train in the Adirondacks ....... 361 

336. Fire Slash.362 

337. Leaves of the Pitcher Plant.366 

338. Diagram of Sundew.367 

339. Venus’s Flytrap.367 

340. Cat-tails and Arrow-heads.368 

341. Water-lilies — Hydrophytes ....... 368 

342. Cross Section of Leaf of Desert Plant.369 

343. Sage Brush — Xerophytes.370 

344. Giant Cacti — Xerophytes.371 

345. Orchid.372 

346. Long-spurred Violet, a Mesophyte ...... 373 

347. Mistletoe.374 

348. Diagram of Mistletoe ..375 

349. Tropical Vegetation.. . . . 377 

350. Potato Wart.383 

351. Normal Grains of Wheat ..384 

352. Grains of Wheat Affected by Black Rust.384 

353. Diseased Heads of Wheat.385 

354. Heads of Wheat Unaffected by Black Rust . . . .386 

355. Diagram of Life History of Red Rust of Wheat .... 387 

356. Variation in Yields of Corn . . . . . . 388 

357. Types of Heads of Oats ........ 389 

358. Irrigating Ditch.391 

359. Irrigating Ditches.392 

360. Hepatica. 394 

361. Fringed Gentian . ..395 

362. Pink Lady-slippers.396 

363. Alimentary Canal of Man.. . 404 












XX LIST OF ILLUSTRATIONS 


FIGURE 

PAGE 

364. 

Tongue of Man. 

. 405 

365. 

Diagram of Taste Cells. 

. 405 

366. 

X-ray of Three Teeth. 

. 406 

367. 

Vertical Section of Tooth. 

. 407 

368. 

Milk Teeth. 

. 407 

369. 

Permanent Teeth ...... 

. 408 

370. 

Pear-shaped Human Stomach .... 

. 408 

371. 

X-ray Photograph of Human Stomach 

. .409 

372. 

X-ray Photograph of Large Intestine of Man, Showing Appendix 409 

373. 

Human Gastric Gland ..... 

. 412 

374. 

Diagram of Villus from Inner Wall of Intestine . 

. 414 

375. 

Census Map of Dairy Cows . . . . 

. 417 

376. 

A Typical Western Wheat Field 

# . . 420 

377. 

A Grain Elevator ...... 

. 421 

378. 

Flouring-mill Where Wheat Is Turned into Flour 

. 422 

379. 

War Garden ....... 

. 425 

380. 

Skeleton. 

. 432 

381. 

Cartilage ........ 

. 433 

382. 

Diagram to Show the Structure of Bone 

. 433 

383. 

X-ray of Hand of Child. 

. 434 

384. 

X-ray of Hand of Adult. 

. 434 

385. 

X-ray of Dislocated Finger .... 

. ' 435 

386. 

X-ray of Broken Femur ..... 

. 435 

387. 

X-ray of the Same Bone after Healing 

. 435 

388. 

Muscles of Upper Leg ..... 

. 437 

389. 

Voluntary Muscle Cells. 

. 438 

390. 

Involuntary Muscle Cells ..... 

. 438 

391. 

Heart Muscle Cells. 

. 439 

392. 

The Lungs and Heart. 

. 443 

393. 

Ciliated Epithelium ...... 

. 443 

394. 

Voice Box or Larynx ...... 

. 445 

395. 

Diagram to Show the Relation of the Diaphragm 

to the Ribs 446 

396. 

Hot-air Heating ....... 

. 447 

397. 

Steam Heating ....... 

. 448 

398. 

Photomicrograph of Blood of Frog 

. 449 

399. 

Diagram to Show How Energy Reaches the Cells 

. 450 

400. 

Organs of Circulation . ... 

. 451 

401. 

Heart. 

. 452 

402. 

Diagram of a Vein, Showing the Valves . . . 

. 453 

403. 

Diagram of Capillaries. 

. 453 

404. 

Main Arteries of Frog ..... 

. 454 










LIST OF ILLUSTRATIONS XXI 

FIGURE PAGE 

405. Main Arteries of Man. 455 

406. Superficial Lymphatics of Arm and Hand . ... 456 

407. Longitudinal Section of Kidney. 457 

408. Diagram of Kidney Tubule ....... 458 

409. Diagram of Skin . 459 

410. A Model Reservoir. 463 

411. A Poor Reservoir . . . 464 

412. Nervous System of Man ........ 467 

413. Nerve Cells .......... 468 

414. Nerve Cells . 469 

415. Diagram to Show Reflex Action . . . . . . 470 

416. Section of Eye .473 

417. How We See the Pencil .474 

418. Plan of Ear . 475 

419. Alcoholic Test . 476 

420. Brain Control . 477 

421. Chart of Heart Pulsation.483 

422. Chart of Heart Pulsation . 483 

423. Chart of Heart Pulsation . 484 

424. Tuberculosis Cure, Summer. 490 

425. Tuberculosis Cure, Winter .491 

426. Milk Diluted to 498 

427. Diagram of Epidemic of Sore Throat ..... 499 

428. Malarial Swamp . 500 

429. X-ray of Foot of Girl Wearing High Heel Shoe .... 502 

430. X-ray of Foot of Girl Wearing a Sensible Shoe .... 503 

431. Male and Female Cooties . 515 

432. Adult Fruit-fly .523 

433. Fruit Parasitized by Fruit-fly .524 

434. Variation in Timothy Heads.527 

435. Variations in Yield of Timothy. 528 

436. Variation in Size of Wheat Heads ...... 529 

437. Heredity in Wheat . 530 

438. Leaf Galls on Grape . 531 

439. Heredity Shown by Comparison ...... 533 





































PORTRAITS OF PROMINENT BIOLOGISTS 

FACING PAGE 

Huxley.20 

Jordan.68 

Agassiz.84 

Audubon.110 

Bessey. 196 

Gray.275 

Sedgwick. 461 

Smith.488 

Howard. 525 


xxiii 

















m ' 


























. \ 

V 

























* 







































































> 





INTRODUCTION 


DEFINITION OF COMMON BIOLOGICAL TERMS 



Adaptation. — Have you ever seen a squirrel run up a tree, 
hurry along the branches, then jump to another tree and 
disappear in the foliage? 

Did it occur to you as 
you watched him that he 
was adapted to the mode 
of life that he 'was lead¬ 
ing? His toes are pro¬ 
vided with sharp, curved 
nails that make it easy 
for him to hold fast to 
the rough bark of the 
tree ; and, when he jumps 
from branch to branch, 
his tail acts as a para¬ 
chute, so that his front 
feet alight first. 

Did you ever notice 
how he holds the nut in 
his front feet and how he 
uses his cutting teeth to 
get the kernel ? The feet 
thus used as hands and 
the teeth used for cutting 
are adaptive features. If 
a squirrel has more food 
than he can eat at once, 
he takes the nuts and buries them in the earth. In doing 
this he uses his front feet for digging a hole in the ground 


Figure 1. 

Notice how the squirrel holds the nut 
with his front feet. What use is made of 
his hind feet at this time ? Are his front 
feet being used as hands or feet ? Com¬ 
pare the tail of the squirrel with the tail of 
a mouse (Figure 120). Of what use to a 
squirrel is a big bushy tail ? Would such 
a tail be useful to a mouse ? Would it be 
a detriment ? Why ? 


1 






2 


INTRODUCTION 


while holding the nut in his mouth. After the hole is dug, 
he pushes the nut into the bottom of the hole with his teeth 
and pulls ( the earth over the nut with his feet. These are 
additional uses of his feet and teeth due to their adaptations. 



Figure 2. 


Notice how the thumb and first two fingers hold the pen securely. The 
flat wrist gives a good sliding surface and the muscles are so controlled 
that the letters are uniform in size and shape. The nails of the fingers are 
adaptations and can be used to pick up small objects. The numerous joints 
in the fingers make the hand more serviceable. How many adaptative 
features of the hand can you think of ? 

Did you ever think of your hand as an adaptation? 
When you use a fountain pen in what ways is the hand 
adapted to the use of this instrument? First, you take it 
from your pocket. Then you take the cap from the pen with 



ADAPT A TION 


3 


one hand, while you hold it with the other. You place the 
cap on the top of the pen, the fingers exerting just the right 
pressure in removing it and forcing it on the pen. Then 
you take the pen in your right hand and start to write. 
The pen point is moved in the proper direction to make 
letters, forming accurate loops and curves because the hand 
has been trained to make these lines as you wish. It has 
become especially adapted to do this work. 

You write a page and take a blotter and press it upon the 
freshly written word. The hand is just the thing to use for 
this work. Suppose you 
make a mistake and wish 
to erase it. An ink eraser 
which you hold with your 
fingers you move back 
and forth with the proper 
force and without tearing 
the paper. Suggest other 
ways in which the hand is 
adapted to the work of 
writing. Think of the 
hand of a violinist as it 
rapidly moves over the 
strings, pressing at the 
right place at the right 
time. This is the work of a wonderfully adapted hand. 
The human hand is the best example of varied adaptations 
that we know of. 

Did you ever think of the seeds of the maple tree that grow 
large winglike vanes on the side? The wind carries these 
seeds away from the parent tree and thus -they have a better 
chance to grow. The dandelion has downy tufts on a 
stem that grows up from the seed coat and carries the 
seed miles away from the place where the parent plant 
grew. 



The different “seeds” in this picture 
are all distributed by wind. What are 
the various devices shown on these seeds 
which enables the wind to carry them ? 




4 


INTRODUCTION 


The cocoanut has a buoyant husk that causes it to float 
in the currents of the ocean perhaps a hundred miles away 
till the waves carry it up on the shore, where it grows into a 
cocoanut tree. Some plants, like the wild geranium, hold 
the seed by a spring that throws the seed several feet, if it 
is touched. These are all adaptations that plants employ in 
making their kind grow. 

Animals and plants have come to occupy places in various 
parts of the earth because they have become fitted or adapted 
to the varying conditions. The main adaptations that have 
to do with the individual are: (1) those that assist in food 
getting, such as the cutting teeth of the squirrel or the sharp 
curved beak of the hawk or eagle (see Figure 99); (2) those 
that aid in self-protection, such as the rapid running of the 
fox or the color of a moth (see Figure 31); and (3) those that 
have to do with their surroundings, such as the fish, which is 
provided with fins for use in moving through the water, or 
the bird that has wings to fly through the air. 

Then there are adaptations that have to do with rivalry 
and the welfare of the young. Among the males of sea lions 
there is great rivalry which ends in the survival of the fiercest 
and strongest and death to the smallest and weakest. These 
contests among the males assure the young of sturdy par¬ 
entage. Tusks, horns, and biting teeth are some of the adap¬ 
tations. Certain fish, most birds, and some insects build 
nests where the young are cared for and given added pro¬ 
tection. The building of nests, together with the behavior 
of the adults during this time, are adaptations for the care of 
the young. 

If we inquire more critically into the way plants and ani¬ 
mals live, we shall see that they have in common other 
features besides adaptations. These are sometimes described 
as the fundamental functions of all living things. We shall 
need to know these before beginning the study of animals 
and plants. These fundamental functions are motion, 


EXCRETION 


5 


nutrition, respiration, excretion, sensation (irritability), and 
reproduction. 

Motion. — All animals can move from place to place or 
move parts of their bodies. The higher animals move with 
ease as a result of highly developed muscular and nervous 
systems. The lower animals are more limited in their 
movements. The simpler plants move about in the water 
and at least the leaves of many of the higher plants 
move toward the sunlight, and the hop-vine and morning- 
glory not only grow but move in a certain direction around 
a pole. 

Nutrition. — This function includes the preparation of 
food so that the animal or plant may have it in the form of 
a solution. This is digestion. Next, the food must be taken 
into the veins of the animal or plant. This is absorption. 
Then the food must be moved to all parts of the animal or 
plant. This is circulation. And, lastly, each part of the 
animal or plant must take from the blood or sap the food 
that it needs. This is assimilation. Nutrition is the term 
under which are described the changes through which food 
passes from the time it enters into solution until it becomes 
a part of the living body of an animal or plant. 

Respiration. -— All animals and plants require energy in 
order to live. Part of this energy comes from the food and 
part from the oxygen used in the process known as respiration. 
As a result of respiration the needed energy is obtained and a 
by-product, carbon dioxide, is formed. Respiration, which 
takes place in every living cell, should not be confused with 
breathing, the process by which the higher animals get air 
in and out of their lungs. 

Excretion. — The formation of by-products in the bodies 
of animals and plants and their removal is called excretion. 
The skin, lungs, and kidneys in animals remove excretions. 
In plants they are not always removed but are isolated 
where they can do no harm. 


6 


INTRODUCTION 


Sensation (Irritability). — Animals are sensitive to heat, 
to pain, to light, and to other outside influences (stimuli). 
Plants, too, respond to light and other stimuli. The response 
of animals and plants to stimuli is called sensation or irri¬ 
tability. It is an important life process or function, for it 
enables them to make the most of their location. Because 
of this function animals and plants are able to adapt them¬ 
selves to their surroundings. 

The foregoing life processes have to do with the life of the 
animal or the plant itself. There is another life process that 
is important in keeping alive the races of animals and plants, 
namely, reproduction. 

Reproduction. -— All animals and plants produce young 
or become extinct. The old die and the young carry on the 
work of the race. The number of animals and plants is 
increased on the earth by means of the life process known as 
reproduction. 

These six fundamental functions or life processes are to be 
found in all animals and plants. In some cases it is difficult 
to study them, for they are hidden or masked by other 
processes, or the animal or plant may be so small that we 
cannot easily make them out. 

Biology is the science that deals with the lives of animals 
and plants. It seeks to understand how they are adapted to 
the kind of life they lead and how they carry on their life 
processes by means of various structures. 

The Parts of Bodies. — These life processes tell us what 
the parts of bodies do, but they tell us nothing about these 
parts themselves. There are five words which are used in 
biology to describe these parts. They are: cell, tissue, 
organ, organ system, and organism. 

1. The Cell. — When the biologist takes apart the plant 
or animal he finds that he can separate the parts until he 
comes to a unit so small that a microscope is necessary to 
see it. These microscopic parts are called cells and are alike 


THE PARTS OF BODIES 


7 


in the following respects: each one has a clear outer portion 
called the cell wall which incloses a mass of substance known 
as protoplasm (pro'td-plaz’m: Greek, protos, first; plasma, 
form). The protoplasm is made up of a substance called 
cytoplasm (si'to-plaz’m : Greek, kytos, hollow place ; plasma , 
form), in which is held a saclike 
body, the nucleus (nu'kle-us: 

Latin, nucleus, kernel, nut). The 
nucleus usually contains one or 
more separate bodies called 
nucleoli (nu kle'o-ll). A cell is 
therefore defined as a mass of 
protoplasm composed of cytoplasm 
and nucleus (Figure 4). 

2. Tissues. — The cells are of 
many shapes and sizes, and in 
the bodies of all but microscopic 
plants and animals they are united 
to help the plant or animal carry 
on its life processes. This union 
of cells to do a certain work is 
called a tissue, and the usual 
definition is: a tissue is a group 
of similar cells that do a similar 
work (Figure 5). 

3. Organs. — In all the higher 
animals the tissues are united into 
skin, arms, stomach, and so on, or 
in plants into leaf, branch, etc. Such structures are called 
organs ; an organ is defined as a group of tissues that do a 
given work in the animal or plant. 

4. The Organ System. — When different organs com¬ 
bine to carry on such a general life process as digestion, 
all the parts that assist in this process are described as an 
organ system, as the system of digestive organs. 



Identify the different parts 
from the description in the text. 
Compare the parts and shape 
of this cell with the cells shown 
in Figure 5. What conclusions 
can you draw ? 






8 


INTRODUCTION 


5. Organism. — Every living thing is an organism. It 
may be so small that the microscope is needed to see it. 
Nevertheless it is an organism. If it is a large tree, like a 
giant redwood, it is an organism. Elephants, horses, and 
men are organisms. 

These five expressions, cell , tissue, organ, organ system, 
and organism describe the parts of plants and animals which 

carry on the six life pro¬ 
cesses referred to above. 
We shall read more about 
them as our study of 
biology progresses. 

Classification of Living 
Things. — Our study of 
biology cannot progress 
far before we see the need 
of classifying animals 
and plants. Animals are 
generally grouped in two 
divisions : invertebrates 
(animals without back¬ 
bone) and vertebrates (an¬ 
imals with backbone). 
Plants are also divided into two groups : cryptogams (flower¬ 
less and seedless plants) and phanerogams (flowering or 
seed-bearing plants). Below is given a detailed reference 
table of these classifications. 



Figure 5. — Similar Cells United to 
Form a Tissue. 


Compare these cells with the one shown 
in Figure 4. 


I. Invertebrates. Animals without a backbone. 

1. Protozoa. 8000 different kinds, as, amoeba, paramoecium. 

2. Porifera. Sponges, 2500 different kinds. Examples, the bath 

sponge and grantia. 

3. Coelenterata. Hydra, corals, and jellyfish. 4500 different 

kinds. 

4. Echinodermata. Starfishes and sea urchins. 4000 different 

kinds. 





SCIENTIFIC TERMS 


9 


5. Worms and wormlike animals. Examples, flat worms, tape 

worms, earthworms. 11,000 different kinds. 

6. Mollusca. The clams and snails. 61,000 different kinds. 

7. Arthropoda. Crabs and insects. 400,000 different kinds. 

a. Crustacea. Examples, crayfish and crabs. 10,000 different 

kinds. 

b. Insecta. Examples, grasshopper, flies, butterflies, bees. 

390,000 different kinds. 

II. Vertebrates. Animals with a backbone. 

1. Pisces. Examples, trout, perch, bass, cod. 13,000 different 

kinds. 

2. Amphibia. Examples, frog, salamander. 14,000 different kinds. 

3. Reptilia. Examples, snakes, turtles, alligators. 35,000 different 

kinds. 

4. Aves. Examples, sparrow, eagle, hawk, crow. 13,000 different 

kinds. 

5. Mammalia. Examples, horse, cow, sheep, monkey, man. 

35,000 different kinds. 

The plants, like the animals, are arranged in general 
groups which, beginning with the simplest, are as follows: 

I. Cryptogams. Flowerless or seedless plants. 

1. Thallophytes. 

a. Algae. 

b. Fungi. 67,000 different kinds. Examples, bacteria, molds, 

puff-balls, toad-stools. 

2. Bryophytes. 

a. Liverworts. 4000 different kinds. 

b. Mosses. 12,600 different kinds. 

3. Pteridophytes. 4500 different kinds of ferns. 

II. Phanerogams. Flowering or seed-bearing plants. 

1. Gymnosperms. Examples, pine, spruce. 540 different kinds. 

2. Angiosperms. Flowering plants proper. 

a. Monocotyledons. Example, corn. 23,700 different kinds. 

b. Dicotyledons. Example, bean. 108,800 different kinds. 

Scientific Terms. — Scientists in America, France, Ger¬ 
many, Russia, and elsewhere are continually studying 
different plants and animals. For their convenience the 
Latin names are usually adopted in advanced scientific 


10 


INTRODUCTION 


works. Thus the English or house sparrow is called Passer 
domesticus, and the American elm, Ulmus americana, so that 
scientists of different countries may always use the same 
term. But in this book we shall use the common -Ameri¬ 
can names of the plants and animals studied. 

Scientific terms include also names frequently referred to 
in science books like this Biology, such as physical and 
chemical change, environment, and energy. 

Physical and Chemical Change. — If a solid piece of ice 
is melted, it becomes liquid water. If the liquid water is 
boiled, it becomes gas (steam or vapor). If the steam is 
condensed, it becomes water, which in turn may again be 
frozen into ice. Any change in a substance which does 
not alter the material of which it is composed is called a 
physical change. 

On the other hand, when oxygen unites with wood, the 
wood may burn, giving off heat and smoke, and ash remains. 
But this ash cannot be united with heat and smoke to form 
the original wood. Such a change as is seen in the burn¬ 
ing of wood is called a chemical change. 

Organic and Inorganic Matter. — It is customary to 
separate chemical compounds which are made in living 
things from those which are made outside the bodies of 
plants and animals. All matter such as wood, sugar, and 
meat, which is made in living things, is called organic matter. 
All matter, like stones and water, which is made outside of 
living things, is called inorganic. 

Environment. — Plants and animals have accustomed 
themselves to live in different parts of the world. Their 
behavior and habits under these varying conditions form 
a most interesting part of the study of biology. The sur¬ 
roundings of plants and animals, that is, the different con¬ 
ditions, the air, water, climate, and soil in which they live, 
are called their environment. 

Energy. — To carry on the fundamental processes of 


ELEMENTS AND COMPOUNDS 


11 


plants and animals, energy is needed. Energy is defined 
as the power to do work. It is produced in animals chiefly 
by the action of oxygen on carbon compounds. Oxidation 
is the source of the larger amount of animal energy. The 
amount of energy is in proportion to the amount of oxidation. 
Heat is a form of energy. 

Conservation of Energy. — The source of all energy on the 
earth is the sun. The heat and light of the sun make it 
possible for plants to grow. Plants store up energy in the 
form of starch, wood, and sugar. Animals eat these stores 
of energy and convert them into the energy of heat and 
motion. 

Coal is stored energy from the plants of ages ago. The coal 
is placed in furnaces and burned. This furnishes energy in 
the form of heat. The heat produces steam, which is con¬ 
verted into energy in the form of motion. This motion may 
be converted into energy in the form of electricity. Elec¬ 
tricity may be converted into light or motion. 

We may sum up in this way. The light of the sun made 
plants grow which were transformed into coal. The coal 
was burned under the boiler, making the steam which ran 
the engine. The engine turned the dynamo and produced 
electricity. This electricity was passed through a small 
wire in an electric bulb and furnished light. The light of 
ages ago is again made into light by this long process. It 
has traveled in a circle, so to speak. Energy may be con¬ 
verted into various forms. Electricity may be changed to 
heat, as in the electric flat-iron; into light, as in the electric 
bulb; or into motion, as in the trolley car. One form may 
be converted or changed into other forms of energy. If 
energy is used in one form, it will appear in some other 
form. Energy cannot be created or destroyed. 

Elements and Compounds. — The bodies of plants and 
animals as well as the earth and air are composed of a great 
variety of compounds and elements. The starch found in 


12 


INTRODUCTION 


wheat, potatoes, and corn is a compound of three elements; 
namely, hydrogen, carbon, and oxygen. Elements cannot 
be divided into simpler substances. Compounds are made 
up of elements in chemical combination. There are thou¬ 
sands of kinds of compounds. Calcium carbonate is a 
compound that makes up a large part of limestone rock. 
Water is a compound made of hydrogen and oxygen. Wood 
is made up of compounds, one of which is cellulose which is 
very similar to starch. There are fewer than ninety ele¬ 
ments known at present, but new ones are being discovered 
from time to time. 

Oxygen, carbon, nitrogen, hydrogen, calcium, and iron 
are the elements that make up the principal parts of plant 
structures and animal bodies. 

Oxygen. — This is a gas. It is uncombined in the air, 
making up one fifth of its volume. It readily combines with 
many other elements. The darkening of unpainted barns 
and fences is an example of the union of oxygen with other 
elements. Opening the draft of a stove or furnace allows 
more oxygen to enter and increases the rate of the com¬ 
bination of oxygen with the coal or wood. This raises the 
temperature. The process of oxygen combining with other 
elements, either slowly as in the rusting of iron or rapidly as 
in the furnace, is called oxidation. Slow oxidation, like the 
rusting of iron, shows little heat at any one time, while 
rapid oxidation produces a greater amount of heat in a given 
time. The amount of heat depends on the rapidity of 
oxidation. 

Oxygen is the most important element in the air. Plants 
and animals must use it to live. Respiration has been 
spoken of as a fundamental life process. Without oxygen 
there could be no respiration and consequently no plant and 
animal life as we know it. 

Carbon. — This element, mixed with oxygen, is the most 
important to plant and animal life. It combines with 


NUTRIENTS 


13 


hydrogen and oxygen to form sugar, starch, fat, and wood. 
Charcoal is a form of carbon. It is made by burning wood 
with a small amount of oxygen. Coal is almost wholly carbon, 
while the diamond is carbon in the form of a crystal. 

Nitrogen. — This element is an inactive gas and it does not 
readily combine with other elements. It dilutes the oxygen 
of the air, making it less active. Nitrogen comprises four 
fifths of the volume of the air. It is an important plant and 
animal food. Nitrates are compounds of nitrogen, oxygen, 
and some other elements. Potassium nitrate is a com¬ 
pound of nitrogen, oxygen, and potassium. Sodium nitrate 
is a compound of nitrogen, oxygen, and sodium. Such 
nitrates are the forms in which nitrogen can be used as plant 
food. Plants are unable to use the nitrogen of the air as a 
food directly. Proteins are animal and plant products that 
contain nitrogen. Proteins are necessary food for animals, 
and animals are dependent on plants to furnish these sub¬ 
stances. See pages 278-280. 

There are other elements that are needed in small amounts 
by animals, such as calcium, phosphorus, sulphur, potassium, 
and iron. The human body is made up of: 


oxygen 

72 

parts 

phosphorus 

1.15 

parts 

carbon 

13.5 

u 

sulphur 

.147 

ii 

hydrogen 

9.1 

n 

potassium 

.026 

ii 

nitrogen 

2.5 

u 

iron 

.01 

ii 

calcium 

1.3 

ii 





Nutrients. — The elements above, while forming the body 
structure, are not taken directly as food. The foods we 
commonly use have these elements in combination with other 
materials. The foods that contain the proper elements are 
spoken of as nutrients. These nutrients are starches, 
sugars, proteins, edible fats, and mineral matter. 

Starch is a nutrient that occurs in many of our foods. 
Potatoes, corn, wheat, rye, rice, and most of the vegetable 


14 


INTRODUCTION 


foods contain large amounts of starch. Starch is easily 
changed to glucose by the digestive fluids. It furnishes some 
of the energy of heat and motion for the body. 

Glucose. — Glucose is a nutrient that occurs in grapes and 
in most other fruits. It is slightly different in composition 
from cane sugar or beet sugar. Starch is always changed into 
glucose by the digestive fluids and never into cane sugar. 
The food value of both glucose and cane sugar is high. 
They are used by the body to furnish the energy of heat and 
motion. 

Enzymes. — In the preceding paragraph it was said that 
the digestive fluids change starch into glucose. For many 
years it was not known what substance in the digestive fluid 
causes it to do this work. Now it is known that certain 
substances called enzymes are the real active agents in diges¬ 
tion. The enzyme that changes starch to glucose is called 
diastase. Pepsin is an enzyme that digests protein. There 
are many other enzymes. An enzyme is not changed by 
digestion, so that a very small amount of it digests a large 
amount of food. 

Proteins are nutrients that are found in great variety in 
our food. The proteins differ from starch and sugar in 
having nitrogen in combination with other elements. The 
characteristic element of protein is nitrogen. Each kind 
of protein has its own name. The protein in wheat is gluten; 
in beans it is legumin. Casein is the protein in milk and 
myosin is the protein in meat. The proteins are necessary 
in building and repairing the cells of animal bodies. If more 
proteins are eaten than necessary for this work, the surplus 
may be oxidized to furnish the energy of heat and motion or 
stored as fat. 

Edible Fats. — The term edible fats is used to include 
both fats and oil. These nutrients are almost wholly energy 
producers. They are used chiefly to produce heat. As we 
go north or south from the equator, we find the native people 


OSMOSIS 


15 


adding ever greater amounts of fats to their diet, until we 
come to the Esquimaux, who eat large quantities of pure fat 
with relish. Large amounts of fat are necessary to keep 
the body warm in the very cold zones. 

Mineral Foods. — Salt is a most important mineral food. 
It is so frequently used to give a flavor to our food that we do 
not realize its real importance. A well-nourished animal or 
plant must have it to a certain amount. Deer travel long 
distances for it. Most of the other minerals are found in 
ordinary food so that it is not necessary to use them as we 
do salt. 

Osmosis. — Foods in the form of solutions must be taken 
into the walls of the stomach and intestines and through the 
cell walls of plants. These structures have no pores that 
we are able to see with a microscope and yet the solutions 
pass through. This passing of food and water through animal 
and plant cells is osmosis. The term osmosis is also used 
when a gas, such as oxygen, passes through the skin or lungs 
into the blood. From time to time further explanations of 
this very complex process will be made. A simple device 
for illustrating osmosis is described in Science , Dec. 12, 1919, 
page 542, by Elbert C. Cole. 










BIOLOGY FOR HIGH SCHOOLS 


PART I 

ANIMAL BIOLOGY 

CHAPTER I 

THE GRASSHOPPER, AN INTRODUCTION TO THE 
STUDY OF INSECTS 

1. Variety of Animal Life. — There are more than six 
hundred thousand kinds of animals in the world. Of this 
large number nearly four hundred thousand kinds are in¬ 
sects. Insects are so widely distributed, have such a great 
variety of form and color, and are so numerous that the age 
in which man lives is sometimes called the age of insects. 
While insects do not have any representatives that are 
large, compared with dogs or horses, they make up in number 
what they lack in size. 

Man’s greatest competitor for the domination of the earth 
has been not the lions, rattlesnakes, or other large enemies, 
but the hosts of small animals of which the insects form the 
largest class. The building of the Panama Canal was as 
much a triumph over the disease-carrying mosquito as it 
was an engineering feat. Even to-day, many parts of the 
earth are uninhabitable because of mosquitoes. 

The potato beetle, the chinchbug, the scale insects, the 
codling moth, the gypsy moth, the grasshopper, the army 
worm, and many others are taking a heavy toll each year 
from the world’s food crop. The activities of these insects 
make food prices higher and it is in the interest of food con- 

17 


18 


THE GRASSHOPPER 


servation that more people should be aware of the common 
facts about insects. To do this it is necessary to get an idea 
of how they grow, how they get their food, what they eat, 
where their eggs are laid, how they reproduce, and how they 
may be controlled. 

If a person studies rather closely the life history, structure, 
and activities of one insect, he has a fairly good idea of the 
great class of insects, for they are all much alike in many 
ways. Insects in some ways are like the higher animals, 
such as the fish, bird, dog, and man. All must have food, 
all must get oxygen, all have some way of self-protection, 
all reproduce, and all sooner or later die of accident, disease, 
or old age. Certain insects live as adults but a few hours, 
while elephants may live a hundred years or more. But all 
die in time and the young must come to take the places of the 
old if their particular race is not to become extinct. 

All insects will be found doing something. Some are 
flying from flower to flower, and you can watch to see what 
they are doing; others are busy on the leaves or the stems, 
and a few minutes of observation will show you whether 
they are friends or foes of the plant upon which you find 
them. The most interesting way to study insects is to 
watch them in their home life, but when this cannot be done, 
they can be well studied in the laboratory. Even in the 
city a surprisingly large number of kinds of insects can be 
collected by a class and brought alive to the laboratory. 

2. The Grasshopper. — The study of animals begins in 
this book with the grasshopper. When during the late 
summer we walk into the fields or along paths lined with 
grass, we are often surprised at the number of grasshop¬ 
pers which jump away as we approach. They are of va¬ 
rious sizes and kinds. Some are small and without wings, 
while others have small but well-formed wings. The 
difference in the wings and in the shape of the body tells 
us that there are various kinds of grasshoppers, 


LIFE PROCESSES OF THE GRASSHOPPER 19 



Figure 6. — Female Grasshopper. 


Notice the position and shape of the modified legs at the end of the 
abdomen. 

FIELD STUDY 


Study living insects. Collect insects, such as grasshoppers, crickets, 
beetles, bees, wasps, flies, moths, butterflies, etc. Place some under 
tumblers and complete your report as follows : 



Whebe Found 

1 Number of 

1 Legs 

| Number of 

Wings 

Size of 

Wings 

Size of 

Third Leg 

Mouth Parts 

bC 

3 

o 

+= 

m 

Weak 

Separate 

TJ 

<D 

to 

B 

House fly . 

On food in the home 

6 

2 

Small 






Grasshopper 

On grass in the field 

6 

4 

Medium 






Moth . . 

On flowers in the park 

6 

4 

Large 







3. Life Processes of the Grasshopper. — The young grass¬ 
hopper must escape being eaten, must find food, must have 
oxygen to breathe, must be able to rid the body of waste 
substances, must be able to see, feel, and taste, must develop 
into an adult, and must do its part in providing for another 
generation of grasshoppers. If the grasshopper fails in any 
one of the first three of these necessities, it is unable to live, 























20 


THE GRASSHOPPER 


and consequently the last and most important work, that of 
providing for the next generation, is not possible. 

LABORATORY STUDY 

Examine a live grasshopper. What are its means of locomotion? 
Compare its jump with its length. If in the same proportion, how far 
could a man six feet tall jump? How does the grasshopper obtain 
food? ' What protection from enemies does it gain from its color? 
Notice the division of the body into three regions : head, thorax (tho'r&ks), 
which has wings and legs, and abdomen (Sh-do'mSn). How large is the 
head compared with the thorax and abdomen ? The body is covered with 
a skin-like substance, known as chitin. This is called the skeleton of 
the grasshopper and because it is on the outside of the body it is termed 
an exoskeleton. How does it protect the grasshopper? When the 
living grasshopper is held between the thumb and finger, it “spits 
molasses.” This is the partially digested food from its crop. 

4. Protection. — When we look closely at the grass¬ 
hopper, we find that it is provided with many adapta¬ 
tions which prevent its being caught and eaten. The 



A drawing to show the more important parts of the grasshopper, all of 
which can easily be seen without the aid of special instruments. 

most important of these are its color and markings. When 
a grasshopper jumps into the grass and remains quiet, its 
color so closely resembles the grass and the sticks that many 
of its enemies overlook it. This is an example of what is 










Thomas Henry Huxley (1825— 189,5) was the father of the 
modern method of studying biology. Up to 1850 information 
about plants and animals was imparted only by lectures. Hux¬ 
ley found that science of his day contained many errors due to 
lack of first hand information on the part of the writers. He 
corrected many of these errors by personal study of plants and 
animals, and devoted years to developing methods of laboratory 
study which enabled the student to gain his information directly. 
To-day these methods are accepted wherever the subject of 
biology is studied. This great English biologist made many 
important discoveries and was awarded numerous honors by his 
countrymen. Huxley showed great skill in putting the conclu¬ 
sions of science into simple language. 







RESPIRATION 


21 


called protective coloration. The grasshopper is further 
protected by a pair of large eyes and by simple ears, which 
are located on the side of the body. By means of these 
sense organs, it becomes aware of the presence of enemies. 
The quickness of grasshoppers in jumping also helps them to 
escape being eaten> 

5. Food-Getting. — The grasshopper has little difficulty 
in finding its food. It eats leaves, and particularly the 
leaves of grass. It does 
not need a keen sense of 
smell, as does the bee, 
which must search for 
flowers. However, the 
grasshopper has special 
smelling organs located 
in its antennae (an-ten'e), 
those long feelers which 
grow out from the head 
like soft horns. 

The mouth parts which 
cut and chew the food 
consist of an upper lip 
and two teeth (mandibles, 
man'di-b’ls). The teeth 
are moved by powerful 
muscles which nearly fill 
the head. These mandibles work from side to side, instead 
of up and down as our teeth do. They are so effective 
that sometimes when grasshoppers become numerous they 
strip the grass of all its leaves, and even destroy growing 
fields of grain. 

6. Respiration. — All animals have some way of getting 
oxygen to every portion of their bodies and of getting rid 
of carbon dioxide. The grasshopper has no lungs such as 
ours, nor does it breathe through its mouth. On each side 



Figure 8. — The Lips and Teeth of the 
Grasshopper. 


These show special adaptations which 
explain their peculiar shape and position. 
See if you can find out how each part is 
used when the grasshopper is eating. 




22 


THE GRASSHOPPER 


of the abdomen are eight regularly arranged, small openings, 
spiracles (spir'a-k’ls), which lead into branching tubes, tracheae 
(tra'ke-e). There are also two spiracles on the mesothorax. 
The branching tracheae are kept open by means of skeleton¬ 
like rings so that the pressure of the muscles and other organs 
cannot flatten or close them. The tracheae continue to 
branch until the subdivisions are so small that they can be 
seen only by aid of the microscope. These fine branches 
extend to the minute cells of which the body of the grass¬ 
hopper is composed. Here the oxygen passes to the living 

protoplasm of the cells 
and carbon dioxide is 
given off to the air 
which is in these breath¬ 
ing tubes. This use of 
the oxygen by the proto¬ 
plasm and the giving off 
of the carbon dioxide is 
respiration. (See Res¬ 
piration, page 5.) 

7. Body Regions. — 
The grasshopper has 
three body regions : the 
head, the thorax, and the abdomen. Each of these regions 
is adapted to particular kinds of work. The head struc¬ 
tures are adapted to food-getting, seeing, and feeling. The 
thorax has appendages for locomotion: walking, jumping, 
and flying. The abdomen is adapted to breathing, hearing, 
and reproduction. 

The Head. — On the front of the head are three simple 
eyes and on the sides of the head two compound eyes. Near 
the simple eyes are two antennae for feeling. The mouth 
has several special parts for food getting. (See Figure 8, 
page 21.) These parts are an upper lip (labrum), and a lower 
lip (labium) for moving the food into the mouth. Inside 



Figure 9. — The Jumping Leg of the 
Grasshopper. 

Why is the femur so much larger in this leg 
than in the one just in front of it ? 




BODY REGIONS 


23 


the mouth is a pair of mandibles for cutting food and a 
pair of maxillae with palps for carrying the food. The hypo- 
pharynx, a sort of tongue, is useful in handling the food. 

The Thorax. — This is the second body region and it is 
composed of three parts. The pro thorax, separate from the 
rest of the thorax, is provided with the first pair of legs. The 



HIND-WING 


Figure 10. — Fore- and Hind-Wings of the Grasshopper. 

How does the grasshopper use each wing ? What becomes of the hind¬ 
wing when the grasshopper is not flying ? 

mesothorax, provided with a second pair of legs and the first 
pair of wings, is not clearly separated from the third part 
of the thorax, the metathorax. This supports the jumping 
legs and the second pair of wings (the flying wings), which 
of all these appendages are the most used, and the most 
serviceable. 

The Abdomen. — This third body region is clearly divided 
into ten segments. The first segment, a partial one, con- 
















24 


THE GRASSHOPPER 


tains the two auditory sacs, and two abdominal spiracles, 
one on each side. Fourteen other spiracles are found on the 
next seven segments, seven spiracles on each side. The last 
two segments have no spiracles. Instead they are modified 
for reproduction. The spiracles are used for breathing and 
the auditory sac, possibly, for hearing. In the female the last 
segment of the abdomen is provided with two pairs of blunt 
spines that serve as an egg-laying device called ovipositor. 

LABORATORY STUDY 

Work out the divisions of the body of the grasshopper: head, thorax, 
and abdomen; the position of eyes. How are the antennae related to 
the eyes? How many distinct mouth parts are there? The teeth or 
jaws are the most useful in getting food. How do the jaws work? 
Sketch the head to show these parts with the mouth open. 

Notice the attachment of the head to the thorax. The head fits into 
the thorax. The loose anterior (front) portion of the thorax is the pro¬ 
thorax (forward thorax). The first pair of legs is attached to it. Sketch 
the prothorax to show it and its legs. The portion of the thorax back of 
the prothorax is divided into two regions: the mesothorax (middle 
thorax) and the metathorax (back thorax). The line between them is 
not clear. Sketch these parts together with the legs and the wings. 
The jumping legs are attached to the metathorax; the outer wings to 
the mesothorax; the inner wings to the metathorax. The inner wings 
are used in flying. The leg of the grasshopper consists of : (1) a small 
section close to the body (the trochanter); a long muscular part free 
from spines (femur); a slender spiny part (tibia); and three segments of 
the foot (tarsus). The last segment of the foot is furnished with hooks 
which help the grasshopper in climbing, while the spines on the tibia pre¬ 
vent slipping as the grasshopper jumps. The large muscles in the femur 
of the last pair of legs, the spines on the tibia, and the hooks on the tar 
sus, are special adaptations which help the grasshopper in various ways. 

Notice the tapering abdomen, composed of ten segments (rings), or 
parts of segments. Notice the depression and membrane in the first 
segment. This is the auditory organ, but it is not a true ear. Sketch 
the abdomen to show its features. The spiracles are located on the sides 
of the abdomen and thorax. 

8. Excretion.- —The gaseous waste', carbon dioxide, passes 
from the body into the spiracles and escapes into the air. 


REPRODUCTION AND LIFE HISTORY 25 


The liquid wastes are collected by urinary tubes that open 
into the intestine. If the grasshopper could not get rid of 
the waste substances that form in the body, it would be un¬ 
able to live. If the grasshopper could use up entirely all the 
substances taken into the body, there would be little or no 
waste products. As the various nutritive substances become 
a part of the body of the grasshopper, some of the energy 
which they contain is so arranged that it cannot be used by 
the living cells of the insect. The grasshopper has organs 
of excretion which remove all these waste substances from 
the body. 

9. Nervous System. — The fundamental life process of 
irritability (sensation) in the grasshopper is performed by 
the nervous system. It consists of nerves and ganglia 
arranged in a row beneath the digestive canal and in the head. 
Nerves connect this central chain of ganglia, which are masses 
of nerve cells, with all parts of the body. On the head are 
found compound and simple eyes, special organs for feeling, 
the antennae, and organs of taste on the mouth parts. By 
means of all these specialized nervous organs, the grass¬ 
hopper is able to see, feel, and taste with a high degree of 
efficiency. Through these senses and that of hearing, it is 
made aware of food and enemies. 

10. Reproduction and Life History. — In the autumn the 
female lays from 25 to 100 eggs in shallow holes which she 
makes in the ground. Some grasshoppers lay their eggs in 
decayed logs. The following spring these eggs hatch into 
small, wingless grasshoppers called nymphs (nim'fs). (See 
Figure 11.) The nymph has a firm outer covering called an 
exoskeleton, which stretches but little with the growth of 
the nymph. Accordingly, at stated periods, the nymph sheds 
this exoskeleton, and grows for a time until it fills a new 
exoskeleton. This shedding or molting continues until the 
fifth and last molt, when the nymph becomes an adult pro¬ 
vided with wings and mature in every sense. 


26 


THE GRASSHOPPER 




Adult grasshoppers may be found during the summer in 
meadows, flying and crawling and feeding on the leaves of 
grass, grain, and other crops. At times the numbers may 
increase to such an extent that considerable damage is done 


Figure 11. — Grasshopper Nymphs of Various Ages. 

How do they differ from the adult? 

by them. The adults mate and the females lay eggs to pro¬ 
vide for the next generation. 

11. Metamorphosis. — All animals which pass through a 
marked change in external appearance as they become full 
grown are said to undergo a metamorphosis (met-a-mor'- 
fo-sis : Greek, meta, change ; morphe, form). These 


12. — Codling Moth Larva (greatly enlarged). 
Compare this immature insect with those shown in Figure 11. 


are more marked in such insects as the ants and bees than 
in the grasshopper. For this reason we speak of two forms 
of metamorphosis — complete and incomplete. 

12. Incomplete Metamorphosis. — The newly hatched 
grasshopper, while very small, looks enough like a wingless 






COMPLETE METAMORPHOSIS 


27 


grasshopper to be identified as belonging to the grasshopper 
family. Its form does not change materially from the time 
it is hatched until it is full sized. Thus the grasshoppers 
become adult by a growing process termed incomplete meta¬ 
morphosis, showing no marked change in form (Figure 11). 

13. Complete Metamorphosis. — Certain other insects, 
for example the codling moth, hatch into caterpillars from 
the eggs that the female lays in the apple. These caterpil¬ 
lars are known as 
larvae (lar've: Latin 
larva, mask). The 
larvae of the cod¬ 
ling moth are the 
“ worms in the ap¬ 
ple.” These larvae 
are not recognized 
from their external 
appearance as young 
codling moths, yet 
that is what they 
are. 

As the larva eats 
a great deal, it 
grows rapidly, molt¬ 
ing again and again 
until it becomes a full-grown caterpillar. It then eats its 
way out of the apple and finds a protected spot often 
under the loose bark where it weaves the silken cover¬ 
ing, the cocoon (ko-kon'), about itself. In this cocoon 
it molts again. After this molt it has neither legs nor 
mouth parts and is known as a pupa. The pupa cannot eat, 
of course, but it continues to breathe. After varying lengths 
of time it molts again and the adult codling moth comes 
forth to fly and feed and prepare for another generation. 
Some larvae that emerge from the late apples spin cocoons 



Figure 13. — “The Worm in the Apple,” a 
Codling Moth Larva. 

What effect does it have on the apple ? 





28 


THE GRASSHOPPER 


late in the fall and remain 
as larvae in the cocoons 
all winter. They pupate 
in the early spring. 

This series of changes . 
through which the cod¬ 
ling moth passes from 
egg into caterpillar, then 
into pupa, and finally 
into full-grown moth, is 
termed complete meta¬ 
morphosis. Ants, bees, butterflies, beetles, and certain other 
insects undergo complete metamorphosis. 

There are a number of different terms used to describe 
the larval stage of insects : 

caterpillars are the larvae of butterflies and moths, 
grubs are the larvae of beetles. 

Larvae “ w ig§ lers ” are larvae of mosquitoes, 
maggots are the larvae of flies, 
currant-worms are caterpillars. 

. measuring-worms are caterpillars. 

14. Structure and Classification of the Grasshopper. — In 

order to understand the grasshopper more fully it is neces¬ 
sary to find its place in the classification of animals. All 
animals that are known have been grouped into classes 
for convenience in study. The grasshopper belongs to the 
large class of animals called Insecta (in-sek'ta: Latin, in, 
in; seco, cut.) 

The insects, as a class, have their bodies divided into three. 
regions—head, thorax, and abdomen. (See Figure 7.) All 
have three pairs of legs, and most of them two pairs of wings. 
They breathe by means of air tubes ( tracheae ). In becoming 
adult, all pass through metamorphosis, either complete or 
incomplete. The insect group is subdivided into ten smaller 
groups or orders. 






ECONOMIC PHASES OF THE GRASSHOPPER 29 


The grasshopper belongs to the order known as Orthoptera, 1 
(or-thop'ter-a : Greek, orthos, straight: pteron, wing). In the 
Orthoptera we find six common families: grasshoppers, 
crickets, katydids, cockroaches, walking sticks, and praying 
mantids. 

15. Economic Insects. — By economic insects, we mean 
those insects which, by their activities, are either helpful or 
harmful to man. By saying that an insect has no economic 
importance we mean that it does not harm us by eating 
things useful to us and that it does not help us in any way. 

The struggle to live is a problem for all animals, for man 
as well as for the grasshopper. All insects must eat, and 
some eat the same things we wish to eat. Such insects we 
call harmful. Others aid the growth of plants by carrying 
the pollen dust from one flower to another; others make 
honey. Such insects are useful. Certain other insects, 
like the fly, carry the germs of disease. These insects are 
particularly harmful, for they cause sickness and death. 

Certain beetles eat dead flesh or bury dead animals 
by tunneling under them. Such insects are helpful. We 
should study insects in order to find out which are our 
friends and which our enemies. It would not do to kill 
all kinds of insects, for in many cases we should harm our¬ 
selves. 

16. Economic Phases of the Grasshopper. — The grass¬ 
hopper eats the leaves of plants, and if there are many grass- 


1 grasshoppers, katydids, crickets 
butterflies and moths 
beetles 
bugs 

bees, wasps, ichneumones, gall flies 

flies and mosquitoes 

dragon flies 

May flies 

stone flies 


(straight wings) 
(scaly wings) 
(shield wings) 

(half wings) 
(membrane wings) 
(two wings) 

(teeth) 

(short lived) 

(net wings) 
(wingless) 

often called siphon-mouthed 


Orthoptera 

Lepidoptera 

Coleoptera 

Hemiptera 

Hymenoptera 

Diptera 

Odonata 

Ephemeridse 

Plecoptera 

Aptera 

Siphonaptera 


30 


THE GRASSHOPPER 



hoppers they cause a serious loss of crops. The plague of 
locusts mentioned in the Bible refers to grasshoppers. In 
some of the Western States years ago the grasshoppers 
came in great swarms year after year and destroyed an¬ 
nually crops estimated to be worth $200,000,000. But 
ordinarily, owing to the activities of their natural enemies, 
the number of grasshoppers does not become alarming. 


Figure 15. — Modern Spraying Outfit. 

This invention enables us to destroy harmful insects on our largest 
trees. There are many different kinds. Every city should have one. 
The farmer who raises apples, pears, and other fruits has to spray his 
trees every season, if he expects to have fine fruit to market. 




QUESTIONS 


31 


Among the natural enemies of these insects that do much 
toward reducing their number are the birds. Some of 
the greatest destroyers of grasshoppers are the quail, blue¬ 
bird, sparrow hawk, butcher bird, crow, red-winged black¬ 
bird, and kingbird. The crows, because of their large size 
and great numbers, probably kill the most grasshoppers. 

Other members of the order Orthoptera, that are harmful, 
are the cockroaches, the nuisances of the pantry, and the 
crickets that eat the roots of plants. There are also tree 
crickets which frequently lay their eggs in raspberry cane 
and this injury kills the cane above the place where the 
egg is laid. 

17. What Has an Animal like the Grasshopper Accom¬ 
plished by Living? — (1) It has used plants as food to build 
a complex body. (2) It has produced more grasshoppers. 
(3) It has used some stored-up food which might have 
been useful to cattle or sheep. (4) It has set free waste 
carbon dioxide which can be used by green plants to assist 
them in making food. (5) When it dies and decomposes, 
its chemical substances are returned to the soil and air to 
be used again by other living things. 

QUESTIONS 

What are the most important things that the grasshopper must do to 
live? 

How is the grasshopper protected? How does the grasshopper 
breathe? How get its food? 

How does the grasshopper begin life ? 

Define metamorphosis. How many kinds of metamorphosis are 
there? Which kind does the grasshopper show? 

Is the grasshopper a friend or an enemy to man ? Why ? 


CHAPTER II 



IMPORTANT AND FAMILIAR INSECTS 

In the preceding chapter we studied the grasshopper, a 
typical member of the Orthoptera. We shall now take up 
several other orders of insects, with most of which we are 
already familiar. 

18. Hemiptera. — Another common order of insects is 
the Hemiptera (he-mip'ter-a: Greek, hemi, half; pteron, 


Figure 16. — Scale Insects Photographed on a Fern Frond. 

The insects are oval in outline and colored so that they look much like the 
green frond upon which they are feeding. 

wing). To this order belong such common insects as the 
cicadas, plant lice, the woolly aphis, and the bane of the 
orchard, the San Jose (san ho-sa') scale. Some of these 
are very harmful. When the San Jos6 scale is allowed to 
feed freely, whole orchards may be destroyed. Plant lice 

32 




CICADA 


33 


injure apple, cherry, and peach trees, and the cabbage plant. 
The several kinds of scale insects which harm orchards may 
be killed by spraying the trees with a solution of lime and 
sulphur. 

19. Cicada. — One of the most interesting insects of the 
Hemiptera is the seventeen-year cicada (si-ka'da), com¬ 
monly called the “ seventeen-year locust.” The name is 
given to it because the nymphs (nim'fs, the immature stage) 
remain in the ground, actively feeding on roots, for seventeen 
years. There is another 
kind of cicada that re¬ 
mains in-the ground for 
thirteen years. 

Every thirteen or 
seventeen years, gener¬ 
ally in the month of May, 
the nymphs crawl out of 
the ground, climb trees 
or fences, and molt into 
adult cicadas. The adult 
females lay their eggs in 
tender shoots of trees, 
causing the shoots to die. 

The young cicadas, after 
hatching in the shoot of 
the tree, go into the 
ground and begin their 
long period of larval existence which lasts thirteen or seven¬ 
teen years. These cicadas are usually found in limited 
areas, but in these areas are very numerous. 

The cicadas which we hear every summer are another kind, 
whose nymph lives in the ground for two years. As there 
are two broods of this species that appear in alternate years, 
the number does not seem to vary from year to year. Birds 
do much towards destroying them, the kingbird, sparrow- 



Figure 17.— Adult Seventeen-year 


Cicada and Nymph. 

These insects, commonly called locusts, 
were abundant in the early summer of 
1919 in the Eastern and Middle-Western 
States. Did you see any of them ? If 
you did not, you will have to wait seven¬ 
teen years before you have another 
chance. There may be other breeds in 
the vicinity. 




34 


IMPORTANT AND FAMILIAR INSECTS 


hawk, butcher bird, and great-crested flycatcher being their 
most common enemies. 

20. Coleoptera. — The Coleoptera (co-le-op'ter-a : Greek 
coleos, shield; pteron, wing) are the beetles. The first pair 
of wings is horny and meets in a straight line down the back. 
The second pair of wings consists of thin membranes. The 
mouth parts are for biting. Among the harmful beetles are 
many wood borers, the May beetles, potato beetles, asparagus 

beetles, and weevils. Some 
of the beneficial beetles are 
the ladybug, which feeds 
on destructive and harm¬ 
ful insects, and the carrion 
beetle, that feeds on dead 
animals. 

The ladybugs are de¬ 
cidedly beneficial. Their 
larvse run over leaves and 
feed on other insects. 
Even as adults they con¬ 
tinue this good work. Hop 
growers appreciate the 
value of the ladybug larvae on their vines, as the ladybugs 
destroy the harmful hop lice. 

Through the investigations of the United States Depart¬ 
ment of Agriculture a certain kind of ladybug (Vedalia) was 
found in Australia, which is the natural enemy of an insect 
pest (cottony cushion scale) that was destroying the orange 
trees grown in California. This scale is a plant insect which 
was imported into the United States on young trees. Being 
freed from their natural enemies (Vedalia) which were not 
imported, they had increased rapidly. The prompt impor¬ 
tation of Vedalia put an end to the increase of the cottony 
cushion scale and they are now of no great economic impor¬ 
tance. 



Figure 18. — May Beetle. 


This is one of the commonest mem¬ 
bers of the Coleoptera. Note the an¬ 
terior wings which are shield-like and 
serve for protection. How do they 
differ from the second pair ? 





LIFE HISTORY OF THE POTATO BEETLE 35 


The bird enemies of the beetle are numerous. Among the 
most important are the ring-necked pheasant recently intro¬ 
duced, the rose-breasted grosbeak, and the quail, which 
feed particularly on potato beetles. The English sparrow, 
cuckoo, and kingbird feed on the weevils. Robins, blackbirds, 
and crows eat the white grubs, the larval stage of the May 
beetles. The woodpeckers destroy great numbers of borers 
by digging holes in the trees where the borers are tunneling. 

21. Potato “ Bug ” or Potato Beetle. — The potato beetle 
arrived in New York State from the West in 1872. Originally 
the beetle was found in 
Colorado feeding on wild 
plants of the potato family, 
whence its name of Colo¬ 
rado beetle. It gradually 
made its way east from 
one potato patch to an¬ 
other, being helped by the 
wild plants of the potato 
family that grew where 
there were no potatoes. 

These beetles were also 
carried by trains that in a 
few hours took them hun¬ 
dreds of miles. 

22. Damage. — The po¬ 
tato beetle eats the foliage 
of the potato plant, thus injuring the size and quality of the 
tubers. This is due to the fact that most of the starch 
stored in the tuber is produced in the leaves and when the 
leaves are destroyed the amount of starch available for the 
tuber is lessened. Spraying must be carried on wherever 
potatoes are grown, to insure a good crop. 

23. Life History of the Potato Beetle. — The adult potato 
beetle passes the winter in the ground. In the spring the 



Figure 19. — Eggs of Ladybug (greatly 
enlarged). 

You will need sharp eyes to find them 
in nature. 





36 IMPORTANT AND FAMILIAR INSECTS 

adults crawl out of the ground and the females lay their 
orange-colored eggs on the under side of the leaves of the 
early potatoes. In about a week or ten days the eggs hatch 
and the larvae eat ravenously. In two or three weeks the 
larvae reach their full size. They make their way into the 
ground, where they pupate for two weeks or longer, depending 
on the temperature. At the end of the resting stage, they 
emerge as adults and the females lay their eggs on the late 

potatoes for a second genera¬ 
tion. The eggs hatch into 
larvae, the larvae pupate in the 
ground, and the adults emerge 
in the fall. At the beginning 
of the cold weather the adults 
enter the ground and hiber¬ 
nate through the winter. 

24. Natural Enemies. — It 
is fortunate that the potato 
beetle has so many natural 
enemies. Adult lady beetles, 
popularly called “ ladybugs,” 
and their larvae kill many of 
them. The ta china-flies lay 
eggs on the potato beetle larvae 
and the young tachina-flies in 
the form of larvae burrow into 
the bodies of the beetle larvae, killing them in great numbers. 
Toads and snakes are enemies of the potato beetle and they 
take a heavy toll of them. The skunk is another enemy 
of the potato beetle, while crows, rose-breasted grosbeaks, 
pheasants, and quail destroy them in great numbers. 

25. Life History of the Monarch Butterfly. — The mon¬ 
arch butterflies arrive in the Northern States from the South, 
usually in June. Very soon the females lay eggs on the 
different kinds of milkweeds. The eggs hatch in a few days, 



Figure 20. — Monarch Butterfly. 


It is here seen feeding on the 
flower of the red clover. What is 
it eating ? 



LIFE HISTORY OF THE MONARCH BUTTERFLY 37 



—the time depending on the temperature — into caterpillars 
that feed on the leaves of the milkweeds. Each caterpillar has 
three pairs of jointed legs near the 
head and five pairs of leg-like struc¬ 
tures along the posterior region 
that serve for clinging. The cater¬ 
pillar (larva) molts and each time 
grows larger but does not show 
any signs of wings like the grass¬ 
hopper. It is merely a larger 
caterpillar. 

Just before the fourth molt it 
attaches itself to a leaf or stem 
and hangs by a knot of silk with 
its head down for a few days until 
it molts for the fourth time. After 
this molt it is a pupa without legs 
or mouth parts. It is yellowish 
green in color, with golden spots. 

During this stage there is a strik¬ 
ing change taking place inside the 
green covering. Wings, new legs, 
different mouth parts with a long 
coiled tongue, and a nervous sys¬ 
tem of a different form are growing 
into working order while this pupa 
hangs so quietly. After a few 
days the green pupa case breaks 
open and the adult crawls out with 
the wings crumpled. Within a few 
hours the wings expand and push 
out the wrinkles and it is ready 
to fly away to feed on the nectar of flowers. This is an 
example of complete metamorphosis. (For explanation of 
metamorphosis see §§ 11, 12, 13.) 


Figure 21. — Larva of the 
Mourning Cloak Butterfly. 

It is gradually transform¬ 
ing into the pupal stage. 

In A notice the curve in 
the body of the larva and the 
attachment at the top. In 
B note that the exoskeleton 
first breaks on the back near 
the head. In C the exoskele¬ 
ton is being forced up toward 
the attachment at the top. 
In D the whole of the larval 
exoskeleton is removed and 
is shown shriveled at the 
right. In E the chrysalis is 
shortening and curving to the 
right. Compare E and A. 
Note that the short projec¬ 
tions on the left of E are not 
on the same side as the feet 
in A. Compare with Figure 
22. In F the chrysalis is still 
further shortened and curved. 




38 


IMPORTANT AND FAMILIAR INSECTS 



Figure 22.— Transformation of Pupa of Mourning Cloak Butterfly 

into Adult. 

In A notice the form of the chrysalis. Notice the points on A towards 
the left. What are they? Do they indicate the position of feet? See if 
this question is answered in C. How does the real position of the feet 
compare with their position in A of Figure 22 ? In D notice the folds in the 
wing near the end. In E notice that the scale of reduction is different. 
The chrysalis cover in E is the same as in the other pictures. The camera 
had to be moved back to include the whole of the butterfly after it had 
fully expanded. 




LEPIDOPTERA 


39 


LABORATORY STUDY 



The adult monarch butterfly has the body divided into head, thorax, 
and abdomen. How do these parts compare in size with the same 
regions in the grasshopper? Compare 
the legs and wings with those of the 
grasshopper. Which of these two in¬ 
sects is better adapted to flying? To 
jumping? Draw the entire animal. 

Draw wings and legs. 

Gently rub the finger on the wing, and 
as the dust comes off, the wing looks more 
like the wing of a fly or bee. The lines 
that run lengthwise of the wing are the 
veins. Draw the wing. 

The mouth parts of the butterfly are 
united into a single long tube which is 
the coiled tongue-like structure, called 
the proboscis (pro-bbs'Is). Unroll it and 
see how its length compares with the 
length of the body. The butterfly uses 
the proboscis to suck nectar from flowers. 

Compare these mouth parts with those 
of the grasshopper. 


26. Lepidoptera. — The Lepi- 
doptera (lep-i-dop'ter-a: Greek, 
lepido-, scaly; pteron, wing) in¬ 
clude the familiar moths and 
butterflies. Some of the members 
of this order, such as the adult 
peach-tree borer, look more like 
wasps than like moths. There are 
more harmful insects in the order 
of Lepidoptera than in any other 
order. Among the particularly 
destructive members are the in¬ 
sects which are commonly called 
codling moths, gypsy moths, 


Figure 23. — Cecropia Moth. 

A , larva; B, pupa; C , co¬ 
coon ; D, adult. How does 
this form of metamorphosis 
differ from that shown by the 
life history of the grasshopper ? 






Figure 25. — Young Tobacco Worm, a 
Caterpillar. 

One of its insect enemies has laid 
eggs in its body which have hatched 
into caterpillars. These caterpillars in 
turn have fed upon the tobacco worm 
until it was time for them to pupate. 
They then ate their way out of the body 
of their host and spun their cocoons 
which are attached to the surface of the 
body. What will happen to the tobacco 
worm ? 


Figure 27. — Larvae of Leaf Miner at 
Work in Elm Leaf. 

The larvae are between the upper and 
lower transparent epidermis of the leaf. 
They have eaten all the inner layers of 
the leaf, see Figure 263. 


Figure 26. — One of the Swallowtail 
Butterflies (not common). 

Notice that the tongue is extended by 
means of loop of wire. This gives an idea 
of the length of the tongue in comparison 
with the body. This tongue enables the 
butterfly to gather nectar from flowers 
with long nectar spurs. 


Figure 24.— Redheaded Wood¬ 
pecker Eating Suet Placed 
in a Hole. 


40 










ENEMIES OF THE LEPIDOPTERA 


41 


brown-tail moths, tent caterpillars, cut-worms, army worms, 
and canker worms. 

But not all the Lepidoptera are harmful. Many of the 
most beautiful moths and butterflies develop from larvae 
that do no particular harm. Their natural enemies, such 
as birds and Ichneumones (lk-nu'mo-nes) (see §31, page 51), 
keep their numbers reduced. Among the more strikingly 
colored butterflies are the black swallowtail, the larvae of 
which feed on celery, parsley, 
and carrots; and the monarch 
or milkweed butterfly. 

As the butterfly goes from flower to 
flower after nectar, its head brushes 
against the parts of the flower that 
grow the pollen dust. The pollen is 
thus carried from one flower to an¬ 
other, and this helps the flower to 
grow better seeds. 

27. Enemies of the Lepi¬ 
doptera. — The numerous ene¬ 
mies of the Lepidoptera prevent 
them from becoming a scourge. 

Chief among these enemies are 
the Ichneumones, members of the 
order Hymenoptera (Figure 43). 

Ichneumon (lk-nu'mon) adults 
lay their eggs on the body of many caterpillars. When 
these eggs hatch into small larvae Ichneumones, the larvae 
eat their way into the body of the large caterpillar, where 
they live feeding upon its body juices. These ichneumon 
larvae are called parasites because they derive their food 
from the caterpillar. The caterpillar which contains these 
ichneumon parasites is called a host. 

The ichneumon parasitic larvae grow rapidly and before 
the caterpillar dies they reach the stage at which they 



Figure 28. — Wingless Female 
of Tussock Mopi. 

She is laying eggs on the co¬ 
coon from which she has just 
crawled. After the eggs are 
laid, she moves around for a 
short time and dies of starvation 
if some bird does not find her in 
the meantime. 




42 


IMPORTANT AND FAMILIAR INSECTS 



turn into pupae. When they are ready to pupate, they eat 
their way out of the body of the caterpillar and spin a cocoon 

which in some cases re- 


Figure 29—Tent Caterpillars. 

They are seen resting during the hotter 
part of the day on the trunk of the apple 
tree. Later in the day they go out and 
eat the foliage. Note the great blankets 
of silk that they have spun on the side of 
the tree. Fortunately most of these cater¬ 
pillars were attacked by ichneumon-flies, 
tachina-flies, and chalcis-flies so that very 
few matured. The year following these 
destructive insect pests did very little 
damage owing to the successful campaign 
of their numerous insect enemies. 


mains attached to the 
body of the caterpillar 
(Figure 25). These par¬ 
asitic larvae so weaken 
the caterpillar that it 
dies. We shall learn 
more of these Ichneu- 
mones later. 

Next to Ichneumones, 
the birds are probably 
the most active enemies 
of the Lepidoptera. 
Many birds live entirely 
upon caterpillars and we 
find birds that seek them 
as food in all stages of 
their development and 
growth. The eggs laid 
on the twigs and trunks 
of trees are eaten by 
chickadees, nuthatches, 
brown creepers, and 
woodpeckers. The larvae 
are eaten by many birds, 
notably by cuckoos, blue¬ 
birds, wrens, blackbirds, 
orioles, blue jays, crows, 
and house sparrows. The 
cocoons and pupae are 


sought by the chickadees, 
woodpeckers, nuthatches, and brown creepers. The adult 
insects are preyed upon by house sparrows, chipping sparrows, 



CODLING MOTH 


43 


and the whole group of flycatchers, including the kingbirds 
and phoebes. 



28. Codling Moth. — The most destructive of the lepidop- 
terous insects is the codling moth, already mentioned as an 
example of metamorphosis. The larvae become adult in , 
April at about the time the early apple trees blossom. The 
eggs are laid on the young apples and the larvae begin to 
eat the growing apple, 
which, as a result in 
many cases, drops to the 
ground. In any event 
the quality of the apple 
is injured. 

After these larvae be¬ 
come mature they escape 
from the apple, spin their 
cocoons, and in a few 
days emerge as adults. 

They mature about the 
time the late apples are 
blossoming or later and 
the females lay their eggs 
either in the blossoms or 
on the small fruit. The 
same damage is done as 
to the early apples, but 
as each mature female 
lays a hundred or more 
eggs and as the most important apple crop is the late 
one, the chief damage is at this time. 

In one year the injury done by the codling moth to the 
apple and pear industry in New York State alone amounted 
to $3,000,000. By applying a spray containing some poison 
just after the petals have fallen, the codling moths may be 
destroyed. The spray should not be used while the blossoms 


Figure 30. — Cedar Waxwing. 
Feeding its young a flying insect. One 
of our most beneficial birds. 




44 


IMPORTANT AND FAMILIAR INSECTS 


are fresh, because then the 
helpful bees which visit 
them are killed, and no 
harm is done to the de¬ 
structive codling moths 
that come later . 1 

FIELD, LABORATORY, OR 
HOME STUDY OF MOTHS 
AND BUTTERFLIES 

These insects are easily col¬ 
lected and are interesting to 
study. From late in the spring 
until October you can find 
larvae and pupae. Some of the 
leaves upon which the larvae 
are feeding should be collected. 

The larvae should be placed in 
jars provided with soil and some 
leaves. Arrange the cocoons 
and pupae which you find as sug¬ 
gested in the following table. 


Cocoon 

Pupa 

Spun with 

Spun with 

Spun with 

Without 

Suspended 

Suspended 

Parasit¬ 

silk only 

a leaf 

hair 

cocoon 

from one end 

from one loop 

ized 









Tent caterpillars spin cocoons and form small brown moths. Celery 
'“worms” hang in a loop and form a black, swallowtail butterfly which 
feeds on the nectar of lilacs and the rhododendrons of city parks. 

The black spiny caterpillars of the willows and elms hang free from 
the knot of silk and form the mourning cloak butterfly. 

Tomato "worms” burrow into the ground and form a large-bodied, 
small-winged moth, a sphinx moth. 

1 The life history of the peach-tree borer may be assigned in this connec¬ 
tion. 



Figure 31. — Protective Coloration. 


Explain how the Army used this scien¬ 
tific fact in the recent war. 





























HYMENOPTERA — THE HONEY-BEE 


45 



29. Hymenoptera — The Honey-bee. — In contrast to the 
Lepidoptera, which, as has been said, are probably the most 
destructive order, we find the Hymenoptera (hy-men-op'- 
ter-a: Greek, hymenos , 
membrane or thin skin, 
pteron, wing) that are of 
the greatest value to man. 

This order includes the 
bees, wasps, ants, Ichneu- 
mones, and the like. The 
honey-bee and the bumble¬ 
bee are the most impor-' 
tant of the bees. The 
honey-bee is valuable for 
its honey and wax, and 
as a distributor of the 
pollen which is necessary 
to produce seed. The 
bumblebee is valuable mainly as a distributor of pollen. 

Honey-bees afford a splendid example of community life 
among insects. In the wild state they live in trees and caves. 
All wild honey-bees in this country have escaped from hives. 


riUUKH GZ. - I C.LLOW OWALLOWTAIL, 

Gathering Nectar from Lilacs. 



Figure 33. — a , Honey-bee Worker ; b , Queen ; c , Drone. 
Twice natural size. 






46 


IMPORTANT AND FAMILIAR INSECTS 


In a honey-bee colony there are three classes of bees, — 
the perfect females or queens, the males or drones, and the 
imperfect females or workers. There are 
generally one queen, a few hundred drones, 
and twenty to fifty thousand workers. 

The queen alone can lay eggs. She can 
lay an unfertilized egg which hatches into 
a drone, or she can lay an egg which is 
fertilized. This fertilized egg hatches into 
a queen or a worker, according to the food 
and the size of the cell which are provided 
by the workers' Thus the decision as to 
whether the young bee shall be a queen 
or a worker rests with the workers them¬ 
selves. They also have the power to 
supersede the queen, or to raise a new 
queen in case of the sudden death of 
the old one. These powers are rightly intrusted to the 
workers — the great majority. 

The eggs are placed by the 
queen in cells, and, after hatch¬ 
ing, are fed by the young workers, 
called nurses. The larva is fairly 
bathed in food. In a few days 
the larva is full grown, and then 
pupates. The workers now cap 
over the cell with wax, and in 
about twenty-one days the young 
bee cuts away the cap and crawls 
out — an adult provided with the 
four wings, mouth parts, antennae, 
and six legs of the honey-bee. 

Workers are provided with the 
sting which is a weapon of both 
defense and offense. The queen 



Figure 35. — a , Honey-bee Egg ; 
b , Young Larva ; c , Old 
Larva; d , Pupa. v 
Three times natural size. 



Figure 34. — Three 
Queen Cells. 

In the brood comb 
of the honey-bee. 






HYMENOPTERA — THE HONEY-BEE 


47 


StinJ glands 


Alkoiine^land 
" of s+in<5 


has a small sting, and the drones have none. When bees 
sting large animals, like men, horses, and dogs, their sting is 
pulled out and with it parts of the internal organs, thus 
causing the death of the 
bee. When bees sting 
other insects, or even one 
another, their sting is 
not lost. 

Sometimes swarms 
which have few bees and 
little honey are attacked 
by bees from other 
colonies. It is a pitched 
ba ttle until the “ robber 
bees ” are beaten back or 
the defenders are them¬ 
selves killed. The sting 
is used in these battles. 

Bees are instinctively 
sanitary. If a large bum¬ 
blebee enters the hive, 
the bees kill the intruder 
and usually, finding him 
too large to be taken out, 
embalm him by injecting 
the sting repeatedly into 
his body. The result of 
this operation is to make 
the bumblebee harmless 
to the colony. Some¬ 
times they cover the body 
of a small, dead animal 
with a case made of propolis (prop'6-lis), a substance the 
bees gather from certain buds. This serves to protect the 
colony from the effects of the decomposition of the body. 



.Lancet of 
sting 


Figure 36. — The Bee’s Sting. 

It is provided with barbs and a small 
amount of formic acid as an adaptative 
feature. Being located at the end of the 
abdomen, it can be turned in any direc¬ 
tion. Notice the barbs on the sting. 
These point backwards and are adapted 
to cling to the surfaces through which it 
is forced. 







48 


IMPORTANT AND FAMILIAR INSECTS 



At irregular intervals during the early spring and summer, 
bees have the peculiar habit of swarming. Several reasons 
for swarming are given by bee-keepers, but no one pretends 
to be certain that he really knows the cause. It is a sort 
of revolt of the bees against their condition. Two of the 

commonest reasons given 
to explain swarming are 
the lack of room for the 
growing colony, and lack 
of food. 

When bees swarm, they 
usually alight on the limb 
of a tree and form a dense 
cluster. Here they hang 
from fifteen minutes to an 
hour before leaving for the 
woods. In a few cases 
bees have remained in this 
“ cluster ” state overnight, 
but usually they are lost 
unless they are collected 
inside of half an hour. 
The swarm consists of a 
large number of adult bees, 
workers, and drones, and 
usually a single queen. 

Various devices against 
swarming have been in¬ 
vented, but the most effective is to clip the wings of the queen 
in order that she may be kept at home, because the other 
bees usually follow her. This is done after the queen has 
taken her “ wedding-flight.” Her wings are clipped close 
to the body, but only on one side. The bees that then 
swarm soon come back and are easily controlled. While 
the bees are still in the air, a clean, empty hive is placed 


Figure 37. — Honey-bees Clustering 
at Swarming Time. 



ADAPTATION SHOWN IN THE HONEY-BEE 49 


where the old one was. Bee-keepers, during the swarming 
period, always have a number of empty hives in position 
ready for the swarm to occupy. 

The returning bees enter the new hive in search of the 
queen. As they are rushing in, the queen with clipped 
wings is released, and she, 
in turn, joins the proces¬ 
sion and enters with the 
others. Having found the 
queen and plenty of room, 
the colony is usually con¬ 
tent to remain. Sometimes 
swarming becomes a mania 
with certain colonies, and 
it is difficult to get them 
to settle down contentedly 
in a hive and make honey. 

Runaway swarms have to 
be watched with great pa¬ 
tience. Bees that have 
been raised for many bee 
generations in man-made 
hives sometimes leave 
suddenly and seek out a 
hollow tree in the forests. 

The length of the bee’s 
life varies. The drones 
are usually killed at the 
end of their first season. Queens live for five or six or even 
ten years. Workers live three or four weeks in the working 
season and several months in the fall or winter. 

The honey and wax produced annually in the United 
States are valued at $22,000,000. 

30. Adaptation Shown in the Honey-bee. — The tongue 
is adapted to getting nectar from certain flowers like apple 



Figure 38. — Capturing a Swarm. 




50 


IMPORTANT AND FAMILIAR INSECTS 




Trochanter 


Tarsus 


Wax 

pincers 


Figure 39 B. 


blossoms, lindens, white 
clover, and sweet clover. 
It is too short to get nectar 
from red clover blossoms. 
The mandibles are adapted 
to gathering propolis from 
buds, also for kneading the 
wax and for polishing 
surfaces. The wings are 
adaptations for the partic¬ 
ular life of the honey-bee. 
In the first place they are 
small, and are not likely to 
be injured when the bees 
are packed closely together 
as in swarm clusters. 
Then, to compensate 
for the small size, they 
are vibrated with great 
rapidity to carry the 
bees through the air 
with a load of nectar 
and pollen. Sometimes 
they vibrate 440 times 
per second. 

The last pair of legs 
is adapted not to jump¬ 
ing, as in a grass¬ 
hopper, but for carrying 
loads of pollen and prop¬ 
olis. These legs are 
flat and thin and pro¬ 
vided with bristles to 
keep the load from slid¬ 
ing off. 


Inner surface of left hind leg 
of worker 








ICHNEUMONES 


51 


31. Ichneumones. — Another 
interesting division of the Hy- 
menoptera includes the Ichneu¬ 
mones. We have already seen 
(page 41) how they help to keep 
the Lepidoptera from becoming 
a scourge. They also furnish 
other interesting examples of 
parasitism. As an illustration 
we may use one of the larger 
ones known as Thalessa. With 
long, thread-like drills this para¬ 
sitic insect bores holes in trees, 
and lays an egg at the bottom 
of the hole. The egg is usu¬ 
ally laid near the burrow of 
one of the larger tree borers, 
the Tremex. 



Figure 40. —Tongue of 
Honey-bee. 

Notice the numerous hairs of 
the tongue and palps. 



Figure 41. — Model Apiary. 









52 IMPORTANT AND FAMILIAR INSECTS 

The larva of the Thalessa makes its way along the burrow 
of the Tremex borer and fastens itself to the body of the 
borer, where it feeds upon the borer and thus kills it. In time 

the adult Thalessa emerges, 
ready in turn to do its part in 
laying eggs which will destroy 
more of these enemies of the 
tree. But if the Thalessa para¬ 
sites kill the Tremex borer be¬ 
fore it has eaten its way through 
the hard wood, then all die to¬ 
gether, because the Thalessa 
cannot cut an opening for itself. 

32. Ants. — The ants are insects which live in large 
families. Each family has many workers, and a number 
of queens and males. Certain kinds have, in addition, their 
soldiers which have strong mouth parts (mandibles). The 
soldiers do the fighting for 
the colony. Some ants 
are winged and others are 
wingless. 

33. Life History of the 
Ant. —In most ant colonies 
there are several queens. 

Unlike the honey-bees, sev¬ 
eral queens live in har¬ 
mony in an ant colony. 

The ant eggs are so small 
that they are scarcely 
visible to the unaided eye. 

The legless larvae hatch 
in a few days, being full 
grown in about two weeks. 

Pupation lasts about two 
weeks. The cocoons are 



Figure 43.—Thalessa Laying Eggs. 
The tree is infested with Tremex. 



Figure 42. — Worker Honey-bee 
Laden with Pollen. 






LIFE HISTORY OF THE ANT 53 

the white objects which are commonly called “ ant-eggs.” 
The adults guard these cocoons which contain the pupae, 
carrying them away to places of safety when the colony is 
disturbed. Sometimes the 
adult workers remove them 
to warmer quarters. 

The males and females 
have wings while the 
workers are wingless. 

34. Behavior. — Many 
interesting facts about the 
honey-bees are well known 
while less attention has 
been paid to the ants al¬ 
though these seem to be 
even more wonderful in¬ 
sects. Some of the inter¬ 
esting facts about ants 
follow: 

1. They build beaten 
roads with tunnels under 
brush piles. 

2. They keep plant lice 
for the sweet fluid they 
exude which suggests the keeping of cattle by man. 

3. They carry these plant lice into their tunnels and 
care for them over the winter season. In the spring they 
carry them out and place them on food plants. 

4. If a nest is attacked by enemies, the soldiers rush 
around and stroke the workers with their antennae. This 
seems to inform them of the attack and they hurry to the 
rescue. 

5. They wrestle and play and sometimes carry one another 
around. It looks like a football game. 

6. They have battles with other colonies. Before a 



Figure 44. — Tremex. 


Just after laying eggs in a tree. The 
larvae of this insect do much damage 
to trees. 



54 


IMPORTANT AND FAMILIAR INSECTS 


battle starts they send out scouts. They await the return of 
the scouts before they begin the battle. 

7. When one colony subdues another in battle, the victors 
take home the larvae and pupae of the vanquished and bring 
them up to be slaves. The slaves seem to be loyal to their 
conquerors and to take great interest in the welfare of the 
victorious colony. 

8. Among certain kinds of ants the slaveholders have 
depended so long on the slaves that they are unable to build 
nests or even feed themselves. If the slaves are taken away, 
the slaveholders starve. The slaveholders are able to fight, 
however, to get more slaves. 

35. Diptera. — The Diptera (dip'ter-a : Greek, di -, two; 
pteron, wing) include such harmful insects as the mosquito, 
house-fly, bot-fly, and cheese-skipper; 
also the beneficial bee-fly, wasp-fly, 
and tachina-fly. 

One of the most important members 
of this group is the common mosquito, 
which lays from two hundred to four 
hundred eggs in a raft-like cluster on 
the surface of the water in any stag¬ 
nant pool or rainwater barrel. These 
eggs are usually laid early in the 
morning and, in favorable weather, 
hatch the afternoon of the same day. The wigglers (larvae) 
keep to the surface when breathing but swim freely in the 
water for food. Food is brought to the mouth by vibrating 
cilia, which keep a current of water passing near them. 
From this water the wiggler collects his food. After seven 
days of this life it becomes a pupa, which, unlike most other 
pupae, can move about. The pupae remain at the surface of 
the water for air but descend by swimming when disturbed. 
The pupa stage lasts for two days, when the adult emerges 
and flies away after its wings are dried. 



Figure 45. — Common 
House-fly. 


DIPTERA 


55 


The time of these changes from 
egg to larva, from-larva to pupa, 
and from pupa to adult depends on 
the temperature. Warm weather 
shortens the time and cold weather 
lengthens it. 

In the United States there are 
three distinct kinds of mosquitoes. 

(1) The common mosquito is known 
by the technical name of Culex 
(ku'leks). It is not known that the 
Culex carries in its body any disease 
germs harmful to men, therefore it 
is regarded as harmless, although a 
source of great annoyance to those 
who frequent the woods or seashore 
during the summer. (2) Anopheles 
(a-nof'e-lez) is the scientific name 
of a second kind of mosquito, which 
is also generally distributed, but is 
not so numerous as the Culex. The Anopheles often carries 
in its body the germs that cause the disease called malaria. 
(3) Stegomyia (steg-o-mi'ya) is a mosquito common in the 
southern part of the United States. It is the insect which 

carries the germs of 
yellow fever from one 
person to another. 

It is fortunate that 
the mosquitoes have so 
many enemies. The 
“ wigglers ” are preyed 
upon by the larvae of 
the dragon flies, by 
small fish, and by water 
Figure 47. — Eggs and Larwe of Culex. beetles ; while the adults 




Figure 46. — Culex and 
Anopheles. 





56 


IMPORTANT AND FAMILIAR INSECTS 


are eaten by nighthawks, martins, bats, and dragon flies. 
Certain diseases caused by plants attack the adults and kill 
them in great numbers. (See Chapter XXIII.) 

The number of mosquitoes can be greatly reduced by 
destroying their natural breeding places in old rain barrels, 
watering troughs, boxes that may hold water, pails, eaves 
troughs, and sink holes. The larger breeding places are 
sluggish streams and swamps. Draining these is the most 
effective method of preventing mosquitoes from laying their 
eggs in such localities. When this is not possible, the surface 
of the water may be covered with kerosene, which kills 
the larvae by preventing them from getting oxygen from 
the air. Frequent applications of oil greatly reduce the 
number of mosquitoes. 

36. The House-fly. — Because of its filthy habits of 
breeding and living and because it comes to the dining room 
and kitchen crawling over the food, the house-fly has come 
to be recognized as a dangerous disease carrier. 

37. Life History. — Each female lays from one hundred to 
one hundred and sixty eggs in stable filth or other refuse. The 
eggs hatch in a day or so into legless larvae. In five to seven 
days, depending on the temperature and the food supply, the 
larvae are full grown. They then pupate for another five to 
seven days. At the end of this time the adults emerge as 
mature flies ready to lay eggs for another generation. This 
continues until cold weather puts an end to their activities. 
Enough generations are produced every year so that a 
single female in the spring could have a million descend¬ 
ants by October if numerous enemies did not make this 
impossible. 

38. Methods of Control. — Every one should support the 
“ swat the fly ” campaign and help reduce the number of 
flies. The few house-flies that survive the winter are re¬ 
sponsible for the millions that swarm about in the summer. 
Their numbers may be reduced by several methods: 


PARASITISM 


57 


1. Begin early to kill the flies that are seen. 

2. Remove all manure piles and make a general cleaning 
up of all refuse, thus destroying their breeding places. 

3. Put fly traps on the covers of garbage cans to entrap 
all those that hatch as well as adults that go in to feed. 

4. Keep many fly traps in operation in or about the house 
during the time of year that flies are active. 

5. Poison those that do come in the house and keep 
fly paper ready for them at all times. 

39. Tachina-fly. — This fly is beneficial to man. While 
it resembles the house-fly in appearance it has differences 
that may be clearly seen. It has long bristles on the abdo¬ 
men and the bristle of the antenna is bare. The tachina-fly 
lays its eggs on such larvae as tent caterpillars, army worms, 
and many other destructive caterpillars. After these eggs 
are hatched the tachina larvae bore into the bodies of the 
army worms or tent caterpillars and there feed until they 
consume them. Many kinds of caterpillars are held in 
check by the activities of these tachina-flies. 

40. Parasitism. — If a plant or an animal feeds on a 
living plant or animal, it is an example of parasitism. In the 
above, the tachina-fly is the parasite and the tent caterpillar 
is the host. The parasite feeds on the host. If it feeds on 
the outside of an animal, like the mosquito, it is called an 
external parasite. If it feeds on the inside of an animal, 
as in the case of the tachina-fly larva, it is called an internal 
parasite. Lice and fleas are external parasites. In some 
cases parasitism is helpful to man, as in the case of the 
tachina-fly; in other cases, it works harm to man, as in the 
case of the anopheles mosquito. 

SUMMARY 

The insects include a large number of animals, the smallest 
of which can be seen only through a microscope, while the 
largest, certain butterflies, measure nine inches across their 


58 


IMPORTANT AND FAMILIAR INSECTS 


wings. Some insects are parasitic and lead dependent lives. 
Insects feeding on plants which we wish to eat are called 
harmful. Others, like the honey-bees and silkworms, which 
make products that we use, are beneficial. Insects such as 
ticks and lice, that injure our domestic animals, are harmful. 
Then there are the beautifully colored moths and butterflies 
whose larvae never become numerous enough to do much 
damage; we say that they are beneficial because we get 
pleasure from their beauty. 

The whole question of what is beneficial or harmful depends 
on the relation of the insect to man. Insects living on an 
uninhabited island could not be thus classified. In the 
earlier stages of our civilization, many insects now regarded 
as harmful were not so classified, because man had not learned 
to use the plants upon which they fed. The important 
relation which insects bear to disease has, in recent years, 
caused us to classify several insects as harmful which were 
not so considered earlier. 

Insects, like man, are constantly undergoing a struggle 
to escape their enemies and to secure food and a place to 
live. It is interesting in this biological study to try to 
view ourselves in the same unprejudiced way in which we 
study the lower animals; it helps us to understand 
ourselves, and to go forth better equipped to wage our 
contest and win our fight. 

QUESTIONS 

Explain the difference between beneficial and injurious insects. 

Which are some of our most beneficial insects? How do they help 
us? 

How did they help to save the orange industry of California? 

How do fruit growers spray their trees? Why? 

What can you do to prevent harmful insects from spreading? 

Describe the habits of ants and compare with honey-bees. 

Name the common flies. What are their food habits ? 

Compare the life history of fly and mosquito. 


REFERENCES 


59 


REFERENCES 

Crary, Field Zoology, Chapter X. 

Folsom, Entomology with Reference to Its Biological and Economic 
Aspects. 

Hegner, Introduction to Zoology, Chapter XII. 

Hodge, Nature Study and Life, Chapter X. 

Kellogg, Animals and Man, Chapter XV. 

Osborne, Economic Zoology, Chapter XII. 

Root, A. B. C. and X. Y. Z. of Bee Culture. 

Smith, Our Insect Friends and Enemies. 


CHAPTER III 


CRUSTACEANS AND RELATED FORMS 

41. Crustaceans. — The Crustaceans (kriis-t a/shuns : 

Latin, crusta, crust) are so called because of their hard 
outer covering. They belong in the same group of ani¬ 
mals as the insects. The body consists of a limited number 
of segments, each of which usually 
bears a pair of jointed appendages. 
The appendages are variously modi¬ 
fied ; some aid in swimming, others in 
securing food, and others are used in 
walking. The jointed appendage is the 
characteristic expressed in the techni¬ 
cal name Arthropoda (ar-throp'o-da: 
Greek, arthros, joint; pod, root of pous, 
foot) given to the group to which all 
these animals belong. 

42. Crayfish. — As a typical crusta¬ 
cean we have the common crayfish, or 

Figure 48. — Crayfish, “ cra b” as it is known away from the 
Showing Eggs. , n . . 

seashore. The crayfish has nineteen 

pairs of appendages adapted to different kinds of work. 
It lives in fresh-water ponds and streams where there is 
sufficient lime for its use in building up its outside covering 
(exoskeleton). 

The animal is divided into two regions, the head-thorax 
region and the abdomen. The segments of the abdomen 
are clearly defined, but those of the head-thorax are so 
fused that they cannot be made out. 

43. Appendages. — The appendages of the head-thorax 
region are the most important to the animal. Certain of 

60 




MOLTING 


61 


these are fin-like and by their constant waving motion 
serve to carry food to the mouth. Others are elongated 
and serve for walking. One pair, the pincers, are used 
for seizing and holding food. 

The last abdominal segment and the appendages next 
to the last are broad and form a tail fin (caudal fin). 

Molting. — One of the interest¬ 
ing features in the study of the 
crayfish is the shedding of the ex¬ 
ternal skeleton. Being covered by 
a firm exoskeleton it is necessary 
that this be removed occasionally, 
in order that the animal may grow. 

Molting, in the case of the crayfish, 
is a serious and dangerous opera¬ 
tion, as it is followed by a period 
during which the crayfish is without 
means of offense or defense. The 
crayfish usually hides until a new 
exoskeleton is partially formed. 

In the molting process the cover¬ 
ing of the eyes and part of the lin¬ 
ing of the digestive tract, as well as 
the whole exoskeleton, are shed. The crayfish molts every year 
of its life and several times during the first year (Figure 49). 



Figure 49. — Molted Exo¬ 
skeleton of Lobster. 

One can tell just what kind 
of an animal this is simply by 
studying this cast-off shell. 


LABORATORY STUDY 

Place several crayfish in jars or aquaria and observe their behavior. 
Fill out the following report: 


Do THEY 
Move the 
Antennae ? 


DO THEY 

Walk 
Forward ? 


Do THEY 
Walk 
Backward 


Do they Use 
? Caudal Fin ? 


Do THEY 
Move Eyes? 


What Organs 
Make a Cur¬ 
rent in 
Water? 















62 


CRUSTACEANS AND RELATED FORMS 


Laboratory study on the appendages. Examine more fully than in 
the above and report the work of each pair of appendages. Compare 
one of the abdominal appendages with those used in walking and feel¬ 
ing. What is the work of the large pincers? How many fin-like 
appendages are found in the mouth region? Notice that one of the 
mouth appendages has a flat part that extends in front of the gills. 
This part of the appendage is called the gill scoop or bailer. Describe 
how the appendages show at least three useful adaptations in the life 
of the crayfish. 

44. Food and Food-getting. — The food of the crayfish is 
both plant and animal, living and dead. One of the simple 
water plants, Chara (ka/ra), furnishes the crayfish with 



Figure 50. — Organs of Crayfish. 

Note that the gills are outside of the body. In the posterior part of the 
abdomen, the muscles have been removed to show the nerve ganglia 
which extend the entire length of the body. 

lime for its skeletons. Shells of snails and their own shed 
skins also help to supply lime. Crayfish seize food with 
their pincers and move it towards the mouth. Small food 
particles are also carried towards the mouth by currents of 
water produced by the mouth parts and the abdominal 
appendages. Particles of food are torn loose by the teeth 
or mandibles. 







EXCRETION 


63 


45. Digestive System. — The mouth is just back of the 
teeth, and connects with the stomach by a short esophagus. 
The stomach is divided into front and back parts. The 
front part possesses a grinding structure known as the 
gastric mill, which serves to shred and crush the food and 
make it ready for digestion in the back part. The liver, 
or digestive gland, pours a fluid into the stomach, which 



Figure 51. — Crayfish, Showing How the Eggs Are Carried. 

This is the position that the animal takes when the eggs are being aerated; 
the rest of the time the abdomen is flexed as in Figure 48. 

prepares the food for absorption by the walls of the stom¬ 
ach and intestines. The intestine begins at the back end 
of the stomach and extends to the last segment. 

46. Respiration. — Crayfish obtain oxygen from the water 
by means of gills which are well covered by the overhanging 
skeleton of the head-thorax region, but are really outside of 
the body. Most of the gills are plume-like in shape and are 
attached to the appendages, but some of them are attached 
to the thorax. Water is made to circulate through the gill 
chamber by means of the gill scoop or bailer. The finely 
branched gill affords a large amount of surface for the ab¬ 
sorption of oxygen. 

47. Excretion. — The organs for excretion of waste are 
the green glands that are found at the base of the antennae. 
Blood going to these glands loses some of the waste which 












64 CRUSTACEANS AND RELATED FORMS 

it has gained in its course through the body. The method 
of purification of the blood in these glands is much the 
same as in the kidneys of the higher animals. 

48. Circulatory System. — The crayfish has a well-devel¬ 
oped heart from which extend several arteries that carry 

blood to the various 
parts of the body. The 
blood returns to the 
heart through veins and 
through several irregular 
ducts called sinuses (si'- 
nus-es). As the blood 
flows through the body 
it loses oxygen and re¬ 
ceives carbon dioxide. 
Fresh oxygen is absorbed 
by means of the gills, 
which, at the same time, pass off carbon dioxide from the 
blood into the water. 

49. The Nervous System. — In the crayfish this is made 
up of a brain, ventral nerve chain, and many nerves. The 
eyes are borne on a pair of short movable 
stalks. The special senses are well devel¬ 
oped, and the sense of taste is keener than 
that of most lower animals. 

50. Life History. — The sexes are dis¬ 
tinct. The males may be distinguished 
from the females by the larger tubular 
appendages on the first and second seg¬ 
ments of the abdomen. The eggs of the 
female are carried for some time by the 
appendages of the abdomen, where they 
pass through their early stages of de- 
velopment. The young crayfish is un- common under 
like the adult in form, and approaches boards and sticks. 




Figure 52. — Soft-shell Crab. 

This is the common form sold in the 
markets. 












ARACHNIDS 


65 


maturity only after passing through many 
changes. 

51. Other Crustaceans. — Shrimps, 
lobsters, and crabs are crustaceans of 
much economic importance, because of 
their food value. The trade in these 
animals amounts to millions of dollars 
each year. In order that these important 
food animals may not become extermi¬ 
nated by careless and excessive fishing, 
the state and national governments have 
attempted to control the numbers taken 
and have also established hatcheries in 
which the eggs are hatched and the young 
protected during the earliest stages of 
their development. 

Crustaceans of less economic impor¬ 
tance are the barnacles which cling to 
rocks, wharves, and ships; the hermit 
crabs that live in the shells of mollusks (mol'liisks); and the 
smaller fresh-water crustaceans such as the Cyclops (sl'klops), 

Daphnia (daf'm-a), and 
Cypris (sl'pris), which are 
barely visible to the un¬ 
aided eye. 

52. Arachnids. — The 

spiders, scorpions (skor'pi- 
uns), ticks, and mites are 
arthropods that are 
grouped together under the 
name Arachnida (a-rak'- 
m-da: Greek, arachne, 

spider). The spiders and 
scorpions have eight walking appendages. The forward 
pincers of the scorpions are mouth-parts, and not walk- 





Figure 55. — Daddy-long-legs. 



(much enlarged). 


This is one of the 
commonest of the 
small freshwater ani¬ 
mals. The two large 
sacs on the abdomen 
are the egg-sacs. It 
is the chief food of 
Hydra and the White- 
fish. 








66 


CRUSTACEANS AND RELATED FORMS 


ing appendages. The harvestman 
(i daddy-long-legs ) is a harmless 
arachnid which does good by de¬ 
stroying inj urious insects. Spiders 
catch insects either by pouncing 
upon them or by entangling them 
in their webs. Scorpions sting 
severely, but the wound, although 
painful, is rarely fatal. Some 
ticks and mites are parasitic on man and beast. 

53. Myriapods. — Another group of arthropods is the 
Myriapoda (mir-i-a'po-da: Greek, myrioi, ten thousand; 
pous, foot), a group which includes animals of many legs 
such as the centipedes (sen'ti-pedz) and “ thousand-legged 
worms.” Centipedes are provided with poison glands, hence 
their bite is fatal to some of the smaller 



Very Common Spiders. 


animals and painful to man. The 
thousand-legged worms are harmless. 


Figure 57. — A Tropical Spider. 

Note the eight legs character¬ 
istic of all spiders. The large size 
of its legs gives it strength to carry 
away prey. 




Figure 58. — a, Thou¬ 
sand-legged Worm ; 
b, Centipede. 


Both these worm-like 
animals are members of 
the large class of Arthrop- 
oda and closely related 
to insects. 










SUMMARY 


67 


Note. Insects have been studied also in Chapters I and II, but it 
should be remembered that they are arthropods. 

SUMMARY 

An animal belongs to the arthropods if it has more than 
two pairs of appendages which have several joints in them. 
They also have an external skeleton which is shed at ir¬ 
regular intervals in order to allow the animal to increase 
in size. The body of the crayfish shows that part of the 
segments have fused to form the head-thorax region. The 
members of this group vary much in size and habits. Lob¬ 
sters and crabs are valuable for food and for this reason 
should not be caught when they are small. 

QUESTIONS 

What kind of animals belong to the crustaceans ? How can you dis¬ 
tinguish one from a worm ? From a hydroid ? Explain why insects are 
arthropods. Which groups of arthropods are beneficial? Which are 
harmful ? What do you mean when you say that an insect is beneficial 
or harmful? 

REFERENCES 

See Chapter II. 


CHAPTER IV 



FISHES 

54. Vertebrates. — All the animals thus far studied are 
grouped together under the name of Invertebrates, because 
they have no backbone. We are now to study the Verte¬ 
brates, animals with a backbone, such as fishes, frogs, snakes, 
birds, and mammals. 

The presence of a backbone in vertebrates is their most 
conspicuous characteristic. The formation of the backbone 


Figure 59. — Perch, an Important Food-fish Common in Nearly All 
Freshwater Ponds. 

is always preceded by the growth of an embryonic group of 
cells that do the work of a skeleton. This embryonic group 
of cells forms a structure which is called the notochord (no'to- 
kord: Greek, notos, back; chorda, cord). In all the true 
vertebrates (such as fishes, frogs, etc.), the notochord is 
gradually absorbed and the backbone takes its place, but 
between the vertebrae it remains as cushions. But in the 

68 








David Starr Jordan was born at Gainesville, N.Y., 1851, and 
is still living. He took his master’s degree from Cornell in 1872, 
his medical degree from Indiana Medical College in 1875, and his 
doctor of philosophy degree from Butler University in 1878. Since 
then he has received the honorary degree of doctor of laws from 
four of the leading American Universities. 

In addition to teaching biology for many years, he has written 
numerous technical and popular books on various phases of biology. 
From 1885 to 1913 he was President first of Indiana University 
and then of Leland Stanford University. During all this time he 
continued his scientific studies He is one of the most eminent 
authorities on fishes in the United States. Dr. Jordan’s life and 
attainments are striking examples of what an American boy can 
accomplish by his own efforts and individuality. 











, 
















% 

















: ' 1 ■ I ' ■ I t 



























































. 








. 



. 





































* 





































































VERTEBRATES 


69 



fish-like animal called Amphioxus (am-fi-oks'iis), the noto¬ 
chord persists and there is never a true backbone. The 
notochord is always found above the food tube and below 
the spinal cord. 

Another characteristic common to all vertebrates is the 
presence of gill-slits. These are external openings on each 
side of the neck that in the fishes allow the water to pass 


Figure 60. — Sunfish or Pumpkinseed. 

The one usually caught by the small boy fisherman. 

over the gills. Such structures are of use only to aquatic 
animals, and yet all vertebrates have them at some time in 
their development. 

In most vertebrates the skeleton is composed of bone. 
There are usually two pairs of appendages (legs, wings, 
or fins) attached to the body at the shoulder and hip. Here 
special bones join the limb to the body. The bones in the 
shoulder are known as the pectoral (pek'to-ral) girdle ; while 





70 


FISHES 


those in the hip are termed the pelvic (pel'vik) girdle. In 
the snakes, only traces of legs are found (Figures 83, 88, 
and 89). 

A further distinguishing feature of all vertebrates is the 
well-developed nervous system, with its large brain. The 
sense organs, eyes, ears, and the like, are also better de¬ 
veloped than in any of the invertebrates. 

Oxygen is obtained by external or internal gills in most 
aquatic animals and by lungs in all other vertebrates. In 



Figure 61. — Brook Trout. 

This is the most highly prized fish among fishermen. It is rapidly becom¬ 
ing extinct except where protected by law. 


many vertebrates the skin is an active agent in the inter¬ 
change of oxygen and carbon dioxide and particularly in 
those animals which have a thin, moist skin like frogs. 

55. Fishes. — The fishes are vertebrates, that is, they 
have a notochord which, as they develop, gives place to a 
vertebral column. There are four large divisions of fishes: 
(1) the lampreys (lam'priz) and relatives, (2) the sharks 
and relatives, (3) the bony fishes, and (4) the small group 
of fishes with lungs. The most important group in numbers 
and economic importance is the bony fishes. This group 




EXTERNAL PARTS OF A FISH 


71 


includes the salmon (sam'un), trout, bass, whitefish, pike, 
shad, menhaden (men-ha'd’n), cod, mackerel, herring, sar¬ 
dine, etc. Typical bony fishes are the goldfish, perch, and 
sunfish (Figures 59 and 60). 

56. External Parts of a Fish. — The external parts of a 
fish show a well-marked head attached directly to the 



Figure 62.—Diagram of External Parts of a Bass. 
These names are used in describing all fish. 


trunk; a trunk region, the largest part of the body; and 
a tail region which is sometimes as long as the trunk. 

In a bony fish the mouth is at the front end of the head. 
The jaw bones, bearing many small, needle-like teeth, are 
not firmly attached to the skull. The side of the head next 
to the trunk is protected by a piece of 
bone that covers the gills (gill cover or 
operculum, o-per'ku-lum). 

The trunk bears a number of fins. 

Each fin is furnished with several bony 
fin-rays covered by a thin fold of skin. 

On the shoulder and hip regions of the 
trunk, the fins occur in pairs and are 
called the pectoral and pelvic fins. Sev¬ 
eral fins are found that are not in pairs. 

These are the median fins of the trunk. 

The caudal or posterior region of the 



Figure 63. — Scales 
of Fishes. 







72 


FISHES 


fish ends in a large median fin. The tail region is chiefly 
important in locomotion, but the fins also help in balancing 
and steering. 

Scales cover the trunk and tail, each one overlapping like 
the shingles of a house. The skin is full of mucous glands 
that keep the fish covered with slime. Both the slime and 
the scales protect the fish (Figure 63). 


LABORATORY STUDY 

Study living fish, such as goldfish or perch. Place one or two in an 
aquarium and observe their behavior. Fill out the report below. 


Number 

Number of 
Paired 
Fins 

Number of 
Unpaired 
Fins 

Which are Used to 

Do THE 
Eyes 
Move ? 

of Fins 

Advance ? 

Stop ? 

Balance ? 









Note the shape and relative position of the head, trunk, and tail 
region. The gills are covered by a bony shield, the operculum. What 
is its size and how attached? Where are the eyes located? Do they 
move? Can the eyes be closed? How is the body covered? Of 
what use is this covering to the fish? 

57. Locomotion. — The bodies of such fishes as are shown 
in Figures 59-61 are adapted to swimming. The tapering 
head offers but little resistance to the water and the general 
spindle-shape of the whole body enables it to move easily 
when completely surrounded by water. Notwithstanding 
that there are paired fins which are similarly placed to the 
paired legs of a frog or dog, these fins are not important in 
giving speed to the fish’s movements. They act as brakes 
when the fish desires to stop, the brake being applied by 
simply straightening out these paired fins at right angles 
to the body. The median fins on the back and lower sur- 






















FOOD TAKING 


73 


face of the body keep the fish from tipping over and are 
chiefly for balancing, the paired fins also assisting in this 
process. The tail of a fish is supplied with a large terminal 
fin. This fin and the tail of the rapidly swimming fish, which 
is often one third of the entire length of the body, is the chief 



Figure 64. —The Gill of a Fish. 

Blood vessels penetrate into the fine gill filaments where the waste 
carbon dioxide is given off into the water and oxygen taken into the 
blood. The gill rakers assist in capturing food. 

organ of locomotion. Movement is produced by a rapid side- 
wise motion of the tail. 

58. Food Taking. — Fishes eat insects, worms, crayfish, 
snails, and other fish. The teeth of fish serve to seize, tear, 
and hold food. None of the fish have teeth which are 
adapted to crushing or chewing the food, as is the case 








74 


FISHES 


among the higher vertebrates, like the dog, horse, and 
man. 

Fishes which eat minute animals and plants have many 
sharp pointed projections on the inside of the gill arches 
which act as strainers and gather quantities of this small 
food as the water passes over, the gills. These projections 
are called gill-rakers (Figure 64). Their development 
seems to vary in proportion as they are needed for service. 
Fishes that feed on crayfish and on small fish have no use 
for gill rakers or strainers and accordingly their gill rakers 
are undeveloped. 

The food captured by the teeth of the fish or caught in 
the gill strainers passes at once into a short esophagus 
which expands into the thick-walled stomach. Here the 
various plants and animals that have been swallowed undergo 
partial digestion, the remainder of the process being com¬ 
pleted in the intestines. The dissolved foods are absorbed 
through the walls of the stomach and intestines by osmosis 
and pass into the blood. The main parts of the digestive 
system and their adaptation *to digestion are the same as 
in all the higher vertebrates. 

59. Respiration. — Water is taken in through the mouth 
and passes out through two openings, one on each side of 
the neck. In each opening four or five gills are found. 
The gills are made up of numerous, small, very short, fleshy 
threads or filaments (Figure 64). Into each filament a blood 
vessel penetrates and here the blood throws off carbon 
dioxide and takes oxygen from the water by osmosis just 
as the blood of the crayfish does. The thin-walled gill 
filaments are adapted to respiration in the water. The 
water is drawn into the mouth and forced out over the 
gills in much the same way as water is pumped from a well. 
When a fish opens its mouth, the water rushes in. As the 
mouth is closed, the floor of the mouth and throat is raised 
slightly, pushing the water against the side of the neck and 


NERVOUS SYSTEM 


75 


through the gill opening. The mouth is thus emptied of 
water so that when it is opened again more water flows in. 

60. Circulation. — The blood of fishes is carried in well- 
defined blood vessels and a heart of two chambers. The 
blood is sent from the heart to the gills, where it is purified 
of carbon dioxide and receives oxygen. It is then carried 
by means of arteries to other parts of the body, where the 
oxygen in turn is given up and carbon dioxide is received. 
The blood from the gills and other parts of the body is re¬ 
turned to the heart through veins. Because the blood of 
fishes is at a lower temperature than the blood of man and 
changes with the seasons, they are called cold-blooded animals. 

61. Excretion. — The waste produced in all parts of the 
body as a result of the use of oxygen in the process of 
oxidation is in the form of a gas known as carbon dioxide. 
This gas is carried in the blood to the gills where it passes 
by osmosis through the thin walls of the gill filaments into 
the water. In addition to oxidation, there are other vital 
processes taking place in all the cells of the body of the fish. 
These vital processes produce waste substances that exist 
in the form of liquids which are gathered up by the small 
blood vessels and carried to the kidneys of the fish. Here 
these liquid wastes are extracted from the blood and are 
cast off from the body. 

62. Nervous System. — The nervous system of a fish con¬ 
sists of a spinal cord and a well developed brain. There is 
no structure in the nervous system of a crayfish that can 
be compared to the brain of a fish. Many nerves connect 
the brain and spinal cord with all parts of the body and 
these nerves belong to the nervous system. Associated 
with a better development of the brain are special sense 
organs. 

Special Senses. — The eye is well developed. It is glob¬ 
ular and projecting, and it is believed to be near-sighted. 
The organs of smell are usually located in the nasal cavity. 


76 


FISHES 


In the bull-head, they are found in the feelers, on the head, 
and even in the skin of the tail. The ear is under the skin, 
and there is no external opening. As water conducts sound 
vibrations more readily than air, no device for gathering 
sound waves is necessary. 

63. Reproduction. — The sexes of fish are distinct. At 
certain seasons many fish migrate upstream to lay their 
eggs (to “ spawn ”). Eggs are laid in large numbers by 
the females, and in the same locality sperm cells are dis¬ 
charged into the water by the males. The sperms unite 



with the eggs. The fertilized eggs hatch after thirty or 
forty days, or longer, depending on the kind of fish and 
the temperature of the water. The yolk of the eggs is 
attached to the young fishes for many days after they are 
able to swim, and supplies all the food they need during this 
time. (Figure 66.) 

The spawning habits of fish must be understood thor¬ 
oughly if they are to be raised artificially, as is done in the 
many fish hatcheries. Most states have scientific game 
laws which protect the fish during their egg-laying period 
when they are easily caught and when the destruction of 
even a few fish means the loss of thousands of eggs. 





FISH HATCHERIES 


77 


Spawning habits vary greatly. Some fish, like the sal¬ 
mon, make long journeys from the sea to the head waters 
of rivers and streams to deposit their eggs. The Colum¬ 
bia River is famous for the number of salmon which spawn 
there. Other fish, like shad, go up a river only a short 
distance to lay their eggs. Many shad, for instance, go 
up the Hudson River in New York state. In the case of 
herring, the eggs are laid in the sea and float on the surface. 

64. Life History of the Eel. — This well-known fish of 
the inland streams and lakes has had so many stories and 
myths in connection with its development that much effort 
has been made to learn the facts. Eels migrate down¬ 
stream to the larger rivers and eventually to the ocean in 
the fall of the year. Here in the region of mud banks the 
females lay their eggs in great numbers and the sperm cells 
of the males fertilize them. In some cases the females lay 
as many as 10,000,000 eggs at one time. After the eggs are 
laid the adult eels remain in the ocean a few weeks and die. 
The young eels pass through the larval stage in about three 
weeks after the eggs s!;art to hatch. 

At the beginning of the second spring the young eels start 
on their trip back to fresh water. Great numbers of them 
may be seen in the spring at the foot of Niagara Falls where 
they are blocked by the great cataract. By crawling over 
stones and along the banks, young eels are able to get above 
ordinary falls in the streams and rivers. 

The eel is a food fish. The commercial value of the eel 
is well known to fishermen. They are rich in oil and highly 
nutritious. Eels vary in weight from three and a half to 
six and a half pounds and often exceed three feet in length. 

65. Fish Hatcheries. — In the natural state, many eggs 
are laid that never hatch because the sperm cells do not 
come in contact with them; and of the fishes that are 
hatched only a small proportion reach maturity. As it 
is a matter of great economic importance that fishes be 


78 


FISHES 


saved from extermination and their numbers largely in¬ 
creased, the governments of the world have established 
hatcheries where fish are raised in great numbers. 

In these hatcheries the eggs are taken from the female 
and placed in a jar, and the mass of minute sperm cells or 



The large mass under the neck is the yolk or food used by the young 
fish before it is able to capture its own food. Note that there are no fins 
and that the gills are not well developed. 


“ milt ” is taken from the male and poured over the eggs, 
so that practically all the latter hatch. Then by giving the 
developing eggs protection, and the young fish sufficient 
and proper food, nearly all these eggs develop into active 
fish and the great loss that comes to the fish developing in 



Figure 67. —Young Fish Seventeen Days After Hatching. 


It has absorbed the large mass of food and the fins and gills are large 
enough to be used by the young fish which must capture its own food 
from now on. 

their natural environment is prevented. When they are 
able to take care of themselves, these fry, as the young 
hatchery fish are called, are taken to natural feeding grounds. 
In New York State and most other states there are state 
hatcheries where such fish as shad, pike, lake trout, salmon, 
brook trout, and others are raised by millions. 
















POSSIBILITIES OF FOOD FROM FISH 


79 


The fish that are most useful as food are taken by hooks, 
nets, and seines, under certain restrictions. Those like brook 
trout which are caught as much for sport as for food can be 
taken only by a hook and line and in certain seasons, the 
season of the year depending upon the time of spawning. 
The brook trout spawns in August and September, while 
the rainbow trout does not spawn until February or March. 

66. Possibilities of Food from Fish. — The United States, 
including Alaska, takes from the water about 2,000,000,000 
pounds of fish, annually. Alaska produces about one fourth 



It is very destructive in its food habits, eating the highly prized food-fish. 

How will the use of this fish for food help the fish industry ? 

of this total. The hatcheries of the United States have an 
output of 4,500,000,000 eggs, fry, and small fish. 

Some of the fish have been caught in too great numbers so 
that they are growing less in number. Some are holding to 
their normal numbers and a few others are increasing. In 
the last class belongs the carp, kingfish, whiting, Pacific 
shad, and Pacific herring. Many edible fish are not eaten 
merely because people do not know about them or perhaps 
are prejudiced. Examples of such fish are sharks, toadfish, 
skates, grayfish, burbot, and menhaden. 

The Carp. — This is one of our most abundant fishes in 
the lakes and inland streams. About 43,000,000 are sold 




80 


FISHES 


each year in this country. Since this species is hardy, easy 
to raise, easy to catch, and has high food value it is desirable 
that more of them be eaten. 

The Gray fish. — The grayfish is found along the Atlantic 
coasts. Although its food value and flavor are equal to 
that of the tilefish and other food-fishes, it has not been 
marketable until recently. Unfortunately, when the fish 
was first named it was called “ dogfish ” from its biting 
habits. With that name people would not buy it. Now 
that it has a better name it is coming into use as a food-fish. 



Figure 69. — The Whiting or Eulachon. 
A food-fish recently placed on the market. 


Its abundance enables fishermen to offer it for a relatively 
small price. 

The Whiting. — This is another good food-fish that has 
only recently been in demand as a food. In 1898 less than 
50,000 pounds were sold, while in 1908 more than 10,000,000 
pounds were marketed. Since that time there has been a 
constant increase in the consumption of this fish. In Eng¬ 
land during 1913 about 70,000,000 pounds were sold at a 
price higher than haddock. The whiting occurs off the coast 
from New York northward. It can be bought fresh, canned, 
salted, and smoked. 

67. Care of Young. — Some fish, like the sticklebacks, 
build nests of sticks and leaves in which the eggs are placed 
and guarded. Bass and sunfish make a circular depression 





SUMMARY 


81 


several feet in diameter near the shore and lay their eggs on 
these so-called “ beds.” These beds are guarded zealously 
by the males, who drive off or carry away crayfish and small 
fish which feed upon such eggs. In former times men sought 
for these “ beds ” and by dropping a baited hook caught the 
bass while defending their eggs. Fortunately this practice 
is now illegal. Generally, adult fish pay no attention to 
their young and in many cases they devour young of their 
own kind as quickly as fish of other sorts. 

SUMMARY 

The term vertebrate is given to all animals that have a 
backbone. All have gill slits, either while developing or as 
adults. Fish have scales and breathe by means of gills. 
Their eggs are usually laid in the water and receive no care 
from the parents. A few fish prepare a crude nest which 
they guard. 

QUESTIONS 

What are some of the structures that all chordates have? 

Why is the word vertebrate used? 

What are the common fishes near your home? 

What ones are sought for food? 

What is being done to keep up the supply of fish in your state ? 

What do fish eat? 

REFERENCES 

Fish Manuals of the U. S. Commission of Fish and Fisheries. 

Jordan, Fishes. 

Jordan and Evermann, American Food and Game Fishes. 


CHAPTER V 


AMPHIBIANS 

68. Amphibians. — Frogs and toads are the best known 
animals of this group; but here belong also the Salamanders 
(sal'a-man-ders), frequently miscalled lizards (see page 99). 

The amphibians (am- 
fib'i-ans : Greek, amphi , 
double ; bios, life) are all 
small, the largest one 
found in America being 
a salamander ( Crypto - 
branchus ), which is rarely 
more than two feet long. 
This term amphibian is 
used to explain the habit 
which frogs, toads, and 
certain salamanders have 
of spending their larval 
(tadpole stage) life in the water and their adult life on 
land, or partly on land and partly in the water. 


LABORATORY STUDY 

Place one or two frogs or toads in a small jar or box and observe the 
points mentioned in the report below. 


DO THEY 
Wink? 

Can they 
Protect 
their Eyes? 

How Do 

THEY 

Get Air ? 

Can they 
Walk? Hop? 

How Do 
they Swim ? 

How Do THEY 
Catch a Fly ? 









Figure 70. — Some Common Salamanders 
Found on Land. 


82 





















HABITAT 


83 


69. Frogs. — There are several kinds of frogs, one of 
which, the leopard frog, is found generally distributed 
throughout the United States. It can be recognized by the 
presence, on the dorsal surface, of many brownish or green¬ 
ish spots, edged with white, which help the frog to escape 
the notice of his enemies as he squats among the water weeds. 
These colors form rather definite bands on the hind legs, 
though there is much variation. The general form of the 
body, the shape of the head, and the long hind legs adapted 
for jumping are much 
the same in all frogs. 

LABORATORY STUDY 

Compare the general shape 
of fish and frog. How do the 
colors differ? Show how the 
legs and feet are adapted to 
the way the frog lives. Is 
the frog sensitive to touch in 
various parts of the body? 

Examine the eyes. Open the 
mouth and see that the frog 
can draw in its eyes. The ear membrane is on the side of the head back 
of the eyes. Pass a probe through the ear membrane of a dead frog 
and see where it comes out in the mouth. This is the opening of the 
Eustachian tube. How far can the living frog see ? Notice the method 
of breathing. See the throat move up and down. Hold the frog under 
the water and gently rub its sides. It will usually croak. Thus we 
can prove that the frog is able to make the air travel from his lungs to 
his mouth and back again while under water. 

70. Habitat. — Frogs are seldom found far from some 
pond or stream on the bank of which they are usually seen. 
When disturbed, they jump into the water, swim to the 
bottom, stir up the mud, and quietly come to rest a short 
distance from the place where they entered. As the nights 
in the fall grow cool, frogs make ready to spend the winter 
in a state of inactivity. During the warmer part of the day 





84 


AMPHIBIANS 


they may be seen sunning themselves on a bank, but as soon 
as ice forms on the water they remain on the bottom or be¬ 
come buried in the mud. The lungs are emptied of air, the 
heart beats decrease, and all the usual life processes take 
place more slowly. This habit of passing the winter in a 
state of inactivity is known as hibernation (hi-ber-n a/shun). 
All the Amphibia, reptiles (Chapter VI, page 99), and sev¬ 
eral of the mammals hibernate during the winter. 

Enemies. —*■ As the frog’s hind legs are considered a deli¬ 
cacy, man is the worst enemy of the frog. Next come 
the snakes, birds, and fish. The leech kills frogs by sucking 
their blood. Fish eat many of the tadpoles, and, strange 
to say, some water beetles eat tadpoles also. 

71. Food. — Frogs are greedy creatures. They will eat 
almost any animal small enough to be swallowed, such as 
insects, worms, snails, tadpoles, and small frogs. These 
are caught alive and when in motion. 

72. Respiration. — The oxygen of the air passes through 
both the skin and the lungs into the blood of the frog and the 
carbon dioxide of the blood is thrown off through these same 
two organs. The frog has large blood vessels close to the skin, 
especially along the back. These send many fine branches 
into the skin. This explains why the frog can “ breathe ” 
through its skin. When the frog remains under the 
water for a long time, as during the winter, all the oxygen 
used enters the blood through the skin. When the air is 
taken into the mouth, it is forced into the lungs by the 
muscles on the floor of the mouth. In a way, the air is 
swallowed into the lungs rather than breathed in as in the 
case of mammals. Experiments have been made which show 
that the frog can get oxygen in sufficient quantities to main¬ 
tain life, even if it has not the use of its lungs. The frog 
thus possesses two organs of respiration, the skin and lungs. 

73. Excretion. — This fundamental life process is per¬ 
formed in the frog as in all other vertebrates. Like the fish, 



Jean Louis Rudolphe Agassiz was born in Switzerland, in 1807, 
and died at Cambridge, Massachusetts, in 1873. Agassiz intro¬ 
duced the laboratory method in zoology to students of America 
and trained many who have be'come prominent in biology. His 
motto, “ Study nature not books,” has been taken as a motto by 
thousands of students all over the world. He was the founder 
of the summer laboratory method of study now so common, the 
first such laboratory having been held at Penikese Island off the 
coast of Massachusetts He was Professor of Zoology and Ge¬ 
ology lit Harvard and Curator of the museum that now bears his 
name. His scientific contributions covered a wide range of sub¬ 
jects in zoology and geology. 













































’ 







































. 
















■s 






















. 



































































































INTERNAL ORGANS 


85 


it has a pair of kidneys that remove the wastes from the blood 
in the form of liquids; while the skin and lungs allow such 
wastes as the gas, carbon dioxide, to be discharged from the 
blood. 

74. Irritability. — In all vertebrates this life process is 
limited to the nervous system, which includes brain, spinal 
cord, nerves, and sense organs as described in the discussion 
of the internal structure of the frog, page 88. Animals 
with definitely developed nervous organs.and a specialized 
brain as in vertebrates are able to do more things than a 
worm, for example. The brain of a frog is really a very simple 
organ when compared with the brain of a dog. This is 
the main reason why a dog can be taught to do so many 
more things than a frog. 

75. Reproduction. — The fundamental process of repro¬ 
duction in the frog family is the same as in all other animals, 
but there is introduced the tadpole stage which makes the 
reproduction of the amphibians different from that of any 
other vertebrate. 

76. Internal Organs. — In order that these several funda¬ 
mental life processes may be better understood in a verte¬ 
brate, ,a knowledge of the structures involved is very 
important. This information will also help you to under¬ 
stand the several organs of man which are discussed in the 
third part of this book. 

Digestive Organs. — The mouth is large. Short lips cover 
the short teeth in the edge of the upper jaw. The tongue, 
which has two fleshy horns at the back end, is attached by the 
front end to the floor of the mouth (Figure 72). The frog 
can throw its sticky tongue over the tip of the lower jaw and 
use the forked end to catch insects which are then carried 
into the back of the mouth. Two groups of little curved 
teeth in the roof of the mouth aid in preventing the escape 
of the prey. The food is swallowed whole. The esophagus 
(the tube connecting the mouth cavity and stomach) of the 


86 


AMPHIBIANS 


frog can be stretched so that a comparatively large animal 
can be swallowed. There is no sharp limit between the 
esophagus and the stomach, which is a long spindle-shaped 
sac (Figure 72), larger than the rest of the digestive tube. 

The small intestine begins at the back end of the stomach 
as a small tube which makes several turns, and finally en¬ 
larges into a region called the large intestine, the last part 
of which is termed the cloaca (clo-a/ca) or common sewer. 



Figure 72. — Diagram to Show the Organs of the Frog. 

Note the relation of the nervous system to the body cavity. The large liver 
is omitted because it would cover the stomach and lungs if inserted. 


Two glands of importance belong to the digestive organs — 
the liver and the pancreas. The liver is a large, dark-red, 
three-lobed organ that covers the ventral (lower) surface of 
the stomach. The pancreas is a whitish, small, irregularly 
shaped body attached between the stomach and the intes¬ 
tine. Both these glands drain into the intestine just beyond 
the stomach. The bile secreted by the liver is at first col¬ 
lected in a sac called the gall bladder. 

All these parts of the alimentary canal are held in place 
by a thin membrane (the mesentery , mes'en-ter-y), one edge 




INTERNAL ORGANS 


87 


of which is attached to the dorsal wall along the line of the 
backbone and the other to the stomach and intestine. A 
small gland (the spleen) is found in this mesentery. The 
spleen has no duct connecting it with any other organ in the 
frog. Blood vessels run through the spleen, which scientists 
believe is important in making new blood corpuscles. 

Lungs. — The lungs are hollow sacs that lie back of the 
stomach, one on each side. In the freshly killed animal, 
these can be filled with air by 
inserting a blow-pipe into the 
windpipe and blowing air into 
them. The empty lungs are 
about as large as the blunt end 
of a lead pencil. 

Kidneys. — The kidneys are 
small red bodies lying close to 
the back. Each one is connected 
with the cloaca by a minute duct 
(ureter or urinogenital duct). 

The urinary bladder is attached 
to the cloaca (Figure 73). 

Reproduction. — The male frog 
has a pair of spermaries (sper'ma- 
riz), one attached to the front 
(anterior) end of each kidney 
(Figure 73). Each spermary (testis) is yellow in color. 
The sperms escape through the kidney. In the female 
frog ovaries, sometimes filled with eggs, are easily seen. A 
long, closely coiled pair of oviducts (o'vi'dukts) opens in 
front near the forward end of the stomach and in the back 
into the cloaca. The eggs break through the wall of the 
ovary and enter the oviducts. As the eggs pass down 
through the oviducts, they are coated with a jelly-like cover¬ 
ing that swells in the water. This jelly covering protects 
the eggs. 



Diagram to show the rela¬ 
tions of the testes to the kidneys 
and the relation of the kidneys 
to the intestine (cloaca). 







88 


AMPHIBIANS 


At the anterior end of each kidney in both the male and 
female frog is to be seen an irregular mass, the fat body, 
which contains stored energy that the frog uses as it begins 
to grow eggs or sperms in the early spring before there is 
plenty of food. 

77. Nervous System. — The nervous system of the frog is 
more highly developed than that of the crayfish. It consists 

of a central part en¬ 
closed in the backbone 
and cranium (braincase). 
This central nervous sys¬ 
tem in all vertebrates is 
always found above the 
digestive tube, and is di¬ 
vided into the brain and 
the spinal cord, from which 
numerous nerves arise and 
extend to all parts of the 
body. 

The parts of the brain 
are the same as in man 
and much easier to study. 
Beginning at the front 
(anterior) end of the brain 
the parts are as follows: 
(1) small olfactory (ol-fac'- 
t6-ry) lobes, which are not 
sharply marked off from 
the rest of the brain, and, 
as shown in Figure 74, 
connect with (2) the cerebral (ser'e-bral) hemispheres, which 
are oval in outline. (3) A short mid-brain region, partly 
covered by the back part of the cerebral hemispheres, con¬ 
nects the front and back part of the brain. (4) Two large 
optic lobes, the widest part of the brain, are just back of 



Figure 74. — Central Nervous System 
of Frog. 








NERVOUS SYSTEM 


89 


the mid-brain. (5) The cerebellum (ser-e-bel'lum) of the 
amphibians is small and easily overlooked (Figure 74). 
The last region of the brain is the (6) medulla (me-dul'la), 
which is occupied by a large triangular cavity called the 
fourth ventricle. 

The work which each of these regions of the brain does 
is not sharply defined. The olfactory lobes receive the 
smell stimuli. The cerebral hemispheres control muscular 
action. When the latter are removed, the frog loses all 
power to initiate any movement and will sit still in a dry, 
warm room for hours unless disturbed. This he never 
does when the cerebral region of the brain is uninjured. 
The mid-brain region is the passageway for all nerve-path¬ 
ways that travel to and fro in the brain. The mid-brain 
and optic lobes explain to the frog the sight stimuli. In 
the frog, the cerebellum, which is poorly developed, is less 
important than in man. The medulla gives off more nerves 
than any other region of the brain. Here are found the 
nerves to the face, tongue, ear, heart, and lungs. While 
there is a great difference between the shape of the parts 
of the frog’s brain and those of man, yet the work done 
by each region is of the same kind. 

The brain joins the spinal cord, without any external 
sign to indicate where one begins and the other leaves off. 
A definite number (ten pairs) of nerves leaves the brain proper. 
These are devoted to the special senses of the head and 
to moving the muscles of the throat and head. The frog 
has ten other pairs of nerves joined to the spinal cord (Fig¬ 
ure 74). In a long salamander there are twenty or thirty 
pairs of nerves on the spinal cord. 

LABORATORY STUDY 

In connection with the study of the frog, the following additional lab¬ 
oratory work should be done in order that the several organs of man 
which are discussed in Part III may be better understood. Frogs that 


90 


AMPHIBIANS 


have been preserved in formalin can be easily dissected. Examine the 
digestive organs: first the mouth, then the esophagus, stomach, small 
and large intestine, and cloaca. For convenience, the liver will have to 
be removed. The pancreas can be seen as a small whitish structure in 
the loop between the stomach and the intestine. The spleen is a round 
red organ usually found near the large intestine. 

A pair of narrow kidneys lies close to the back and is connected by 
ducts with the cloaca. The spermaries are found attached to each kid¬ 
ney near the front end and the sperm cells escape to the exterior by the 
kidney ducts. In the female frog the large ovaries occupy most of the 



Figure 75.—Frog Eggs. 


space of the body cavity. A pair of oviducts opens into the body cavity 
just back of the stomach. The eggs escape from the ovary into the body 
cavity. 

The nervous system is enclosed in bone that is easily removed from 
the dorsal surface. The brain should be studied and the following 
divisions recognized: cerebral hemispheres ending in front in the ol¬ 
factory lobes, which are not clearly marked. Just back of these the 
two large roundish optic lobes which are attached to the midbrain 
{thalamencephalon, thal-a-men-ceph'a-lon). The cerebellum is small, 
and the medulla passes into the spinal cord without any sharp dividing 
line. 

78. Development. — Late in March and early in April 
the frogs gather in ponds to lay their eggs. The eggs are 
surrounded by a jelly-like substance which holds them to¬ 
gether. As the eggs are being laid by the female frog, the 
male frog spreads a large number of sperm cells over the whole 















DEVELOPMENT 


91 


Eflg Nucleus Sperm cell' Sperm Nucleus Fused Nucleus 



Figure 76. — Diagram Illustrating Fertilization in Frog Egg. 

a, The sperm cell is penetrating the cytoplasm of the egg; b, the head of 
the sperm cell has become transformed into a nucleus; c, the egg-nucleus and 
the nucleus derived from the sperm head fusing. This fusing is fertilization. 


mass. These sperm cells make their way through the soft 
jelly and one of them must enter each egg or it cannot grow 
into a tadpole. 

As soon as the sperm cell enters the egg (Figure 76), it 
begins to change from a solid, pointed body into a round 
nucleus which is so much like the nucleus already in the egg 
cell that none but experts 
in this study can tell which 
came from the sperm cell 
and which from the egg 
cell. These two nuclei 



come in contact and unite, 
leaving but one nucleus in 
the egg (Figure 76). This 
last change is fertilization, 
which is defined as the 
union of the contents of 
the egg and the sperm 
nucleus. After this union 
is completed the egg be¬ 
gins to divide into cells, as 
shown in Figure 77, and 
finally a tadpole is grown. 



d e f 


Figure 77. — Dividing Egg of Frog. 

After the egg has been fertilized as 
shown in Figure 76, the embryo begins to 
divide in a regular manner, a, Two-celled 
embryo; b, four-celled embryo ; c, eight- 
celled embryo; d, thirty-two to forty-eight 
celled embryo; e, many celled stage; 
f, embryo beginning to form central nerv¬ 
ous system. 




92 


AMPHIBIANS 


As soon as the young tadpole hatches, it attaches itself 
to plants and lives for the first few days upon the food- 
yolk within its own body; the mouth forms, and horny 
jaws develop. Then the tadpole begins to feed upon minute 
plants and becomes dependent upon its own skill to get food 
and escape its enemies. 

For a time the tadpole breathes through gills. Two sets 
are used. The first ones are on the outside of the body and 
last for only two or three days, when internal gills form in the 
throat and the tadpole breathes much like a fish. 



Figure 78.— The Embryo Becoming a Tadpole. 


The Tadpole Becomes a Frog. — In the growth of the 
tadpole into a frog the hind legs appear first. Later the 
front ones begin to show and as they develop the tail is grad¬ 
ually absorbed. While these external changes are going on, 
there are many complicated internal changes taking place; 
internal gills are disappearing and lungs, nerves, blood ves¬ 
sels, and muscles are being formed to give the new legs life 
and action. The internal lungs take the place of the gills 
in the throat before the legs are fully grown and such tadpoles 
must rise to the surface to breathe air. Explain in Figure 
79 which tadpoles breathe by lungs, and which by gills. 
This complicated way of growing into a frog is called meta¬ 
morphosis and this term has the same general meaning as 
when used to describe the growth of insects (page 26). 

The tadpoles of leopard frogs become small frogs in a 






LIFE HISTORY OF THE TOAD 93 

single summer, but the tadpoles of bullfrogs and green frogs 
require two seasons to complete their development. These 
latter tadpoles hibernate in the mud with adult frogs and 
toads. 

79. Life History of the Toad. — In many respects the 
toad’s life history is similar to that of the frog. The eggs 


Figure 79. —Tadpoles. 

The smallest tadpole, black, on the bottom of the aquarium jar is a toad 
tadpole about three months old. The other two tadpoles on the bottom are 
frog tadpoles about three months old; while the two tadpoles with legs are 
frogs. The larger is about one year old and the smaller three months old. 
This marked difference in size and growth is natural as each kind takes a 
different length of time to go through metamorphosis. 

of the toad are laid in stagnant water in strings of a jellylike 
substance. (Figure 80.) The eggs hatch in from five to ten 
days into wriggling tadpoles, which feed on the microscopic 
plants that are found in water. They swim by means of 
their tails. Respiration is accomplished by means of the 
outside gills which allow the oxygen from the water to reach 
the blood and the carbon dioxide to enter the water. Later 
the inside gills take over the work of the outside gills and the 






94 


AMPHIBIANS 


outside gills disappear. Still later, as lungs begin to develop, 
the tadpoles come to the surface for air so that for a time they 
are getting the oxygen both from the air and the water. 
(See Figure 79.) 

About this time the hind legs begin to appear, the tail 
shortens and, soon after, the front feet may be seen. By 
the first of July the tail has entirely disappeared and the 
small toad begins to hop around on the bank, having the 
form, attitude, and habits of the toad as we see him in the 
garden. From the bank they begin to travel away from the 
water and scatter over the country in all directions. After 



Figure 80. — Different Stages in the Life History of the Toad. 


a rain or during a shower, thousands of them are sometimes 
found hopping along a ravine or highway. Here they are 
run over by man and beast and fed upon by crows and other 
enemies. Of the hundreds that leave the pond but very 
few ever live to be a year old. Since toads feed on a great 
variety of harmful insects they are recognized as beneficial 
animals. Although slow moving, the toad is able to feed 
upon many flying insects which he strikes with his quick 
moving tongue, as they rest on plants or crawl over the 
ground. 

The study of the changes through which the egg of the 
frog grows into a tadpole and then into a frog tells us much 
about the way frogs may have developed from fishes. The 






LIFE HISTORY OF THE TOAD 


95 



tadpole breathes and eats like a fish; but as soon as lungs 
and legs are formed, it breathes and eats like a frog. This 
same study of the tadpole also illustrates how animals may 
gradually have come to live on land. In the early history 
of the earth there were hundreds of animals and plants which 
are no longer known to science. The skeletons, foot-prints, 
and whole bodies of many of these are preserved in the rocks. 
Such remains are called fossils. 

If all the animals, or one of each kind, had been preserved 
in the rocks, it would be easy to investigate these earlier 


Figure 81. — Fossils. 

On the right a fossil leaf that grew on a sassafras tree; on the left a group 
of fossil animals that once were abundant but have become extinct. 

animals and their relation to the living animals of the present. 
But in our information there are great gaps, which we are, 
however, gradually bridging. Apparently unrelated ani¬ 
mals have resemblances, so that in time we may come to 
see that all animals are really related forms, varying only 
in complexity of structure. . One thing that we must always 
keep in mind is that the plants and animals which live now 
are but a small fraction of those which have lived. The rocks 



96 


AMPHIBIANS 


have preserved the remains of only a small part of the forms 
of the past. Many of the records of extinct animals and 
plants have been destroyed by decay and heat so that much 
that would be valuable in solving the question can never be 
found. 

The study of the development of the frog also illustrates 
two other general subjects, heredity (he-red'i-ty) and en¬ 
vironment (en-vl'riin-ment). 

80. Heredity. — The tendency of all young animals to 
grow and live like their parents is called heredity and may 
be defined as the transmission of physical and mental traits 
from parent to offspring. There is no difficulty in recog¬ 
nizing the new frog as a certain kind of frog. The color 
markings on the skin are like those of the parents; it grows 
to about the same size; it eats the same kind of food, and 
lives in the same region. 

Every species of living thing is able to produce new forms 
like itself, and heredity is always at work when new plants 
and animals are being produced. Heredity is best thought 
of as that quality of living matter which expresses itself in the 
growing plant and animal by making sure that it resembles 
its parents. Thus heredity determines that leaves of the 
right shape and size occur in the proper place or that fins 
in the fish or arms in the frog shall form in their normal posi¬ 
tion. The subject of heredity in its relation to man is pre¬ 
sented in the chapter on Human Progress in this book. 

A detailed statement of the laws of heredity is beyond the 
province of an elementary book, but it is now well estab¬ 
lished that certain traits of parent plants and animals are 
reproduced in their offspring in regular and definite amounts 
and proportions. 

81. Environment. — This word is used in two ways. 
First, it refers to general surroundings such as temperature, 
moisture, and seasons, as they vary from year to year; and 
secondly, to immediate surroundings. The frog responds 


ECONOMIC VALUE OF AMPHIBIANS 


97 


to the first by hibernating in the winter; while the second 
phase of environment may be illustrated as follows: the 
tadpole can live only in water, and if the pond dries up be¬ 
fore the frog stage is reached, the environment has been un¬ 
suited to the tadpole. This often happens when the eggs 
are laid in a temporary roadside pond which evaporates long 
before the tadpole becomes a frog. All such tadpoles die 
unless they are able to 
swim to some other body 
of water. 

The birds that are able 
to fly avoid hibernating in 
the winter. They are able 
to adapt themselves to the 
change in the seasons with¬ 
out burying themselves in 
the mud as the frogs do. 

Some of the birds do 
not migrate, but remain 
all winter in the North. 

They have become so well 
adapted to conditions that 
they are able to get their 
food where birds that mi¬ 
grate would starve. 

Man is the only animal 
that is able to live any¬ 
where on the face of the 
earth under the most varied conditions. To realize this 
fully we have but to think of the different surroundings 
of the Eskimo, Indian, Bushman, and of ourselves. 

Each animal and plant is directly dependent upon its 
environment for food and a home. 

82. Economic Value of Amphibians. — The toad is the 
only member of the amphibian group that is of any great 



Figure 82. —Tree Frog. 


Note the disks at end of toes. Com¬ 
pare the environment of leopard frog 
and tree frog. 



98 


AMPHIBIANS 


value to man. It destroys many insects. Frogs eat a few 
but hardly enough to entitle them to high rank as beneficial 
animals. Their chief value is as food and as convenient 
forms for dissection in biology courses. 

SUMMARY 

The amphibians are an interesting group which illustrates 
how water animals may have become land animals. The 
frog has well-developed sense organs, legs modified for jump¬ 
ing, and feet for swimming. The skin is moist and helps 
to serve as an organ of respiration. The color markings 
and the habits of the frog serve to protect him from many 
of his enemies. 

QUESTIONS 

What animals belong to this class ? How can you tell them from 
fish? 

Where do the amphibians of your region five ? How many kinds do 
you know? 

See how many kinds of amphibian eggs you can find. 

How long do tadpoles live before they become frogs ? 

What do frogs and toads eat? 

What is fertilization? Metamorphosis? Evolution? Heredity? 
Environment ? 


REFERENCES 

Dickerson, The Frog Book. 

Hodge, Nature Study and Life. 
Holmes, Biology of the Frog. 
Marshall, The Frog. 

Morgan, Embryology of the Frog. 


CHAPTER VI 



REPTILES 1 

83. Reptiles. — Among the Reptiles (rep'tilz) are in¬ 
cluded lizards, snakes, alligators, turtles, and crocodiles. 
The Reptilia (Latin, repo, to crawl) are characterized by a 


Figure 83. — Rattlesnake — Poisonous. 

Notice the triangular shape of the head and the small pit on each side 
of the nose. Compare with Figure 88. 

covering of bony plates, or scales, in the skin, by the absence 
of gills in the adult stages, and by the presence of lungs. 

84. Life History. — Unlike the amphibians, the reptiles 
hatch directly into their adult form, only much smaller. 

1 If desired, this chapter may be omitted without affecting the sequence in 
the book. 


99 





100 


REPTILES 




Figure 84. — Common Snapping iurtle. 


The young snake just out of the egg or the young alligator 
just hatched is recognized by its resemblance to its parents. 

There is no metamorphosis, as in the frog. The reptiles 
lay their eggs in protected places and exhibit no parental 
care for the eggs or for the young. Some snakes hatch their 

young in the body of 
the parent and the off¬ 
spring are born alive. 

85. Turtles. — Tur¬ 
tles are easily recog¬ 
nized by their outer 
skeleton. This skeleton 
is unlike the skeleton 
of the starfish or crab, 
or of any other group 
of animals. The skele¬ 
ton of the turtle, com¬ 
posed mostly of skin plates, is something like a box with 
a cover, "the upper portion corresponding to the box itself, 
and the lower portion to the cover. The box does not fit 
closely all the way around, for there are places where the 
head, the tail, and the four 
legs stick out. When the 
turtle is disturbed, the legs, 
the head, and the tail are 
drawn inside, and the box 
is pulled down tightly by 
muscles to meet the cover. 

The term turtle is often 
applied to aquatic forms, 
and the term tortoise to 
those living on land. Sea 
turtles attain a length of six or eight feet and weigh some¬ 
times as much as a thousand pounds. The flesh of the green 
turtle and of the terrapin (ter'ra-pm) is used for food. 


Figure 85. — Head of a Rattlesnake. 
Dissected to show the poison gland, a, and 
its relation to the tooth. (Duvermoy.) 






SNAKES 


101 


6. Lizards. — There is a great variety of lizards. A 
common lizard is the chameleon (ka-me'le-un), which has the 
power of changing the intensity of the color in the skin 
by moving the color material nearer the outer surface or 
drawing it away. The 
horned toad of the West¬ 
ern United States is a 
lizard with scales of vary¬ 
ing length which give it 
a horny appearance. 

Horned toads, instead of 
laying eggs, have the 
eggs hatched while yet 
in the oviducts and the 
young horned toads are 
born alive. A poison¬ 
ous lizard is the Gila 
(he'la) monster that oc¬ 
curs in New Mexico and 
Arizona. It has the poison glands in its lower jaw. 

87. Snakes. — Snakes are legless vertebrates with long, 
cylindrical bodies covered with scales. They move by 
means of the scales (scutes) on the under side of the body. 
Most snakes lay eggs, but a few bring forth living young. 

Since snakes eat insects, 
frogs, mice, rats, and rab¬ 
bits, they should be con¬ 
sidered beneficial. 

Rattlesnakes 1 and cop¬ 
perheads are the most 
common poisonous snakes 
of our country. Their jaws are provided with fangs (Figure 
85), by means of which a poison is injected into their prey. 

1 The two most common rattlesnakes are the mountain rattler and the 
massasauge (mas-sa-sa'ge) 



Figure 87. — Rattles of Rattlesnake. 



Figure 86. — Horned Toad, a Lizard. 
Native in western part of United States 
and Mexico. 









102 


REPTILES 


Large snakes like the black snake or blue racer of the United 
States, the boa constrictor of South America, and the python 
(pl'thon) of Asia are constrictors. They are able to wind 
their bodies around their prey and to crush it to death. 
The most deadly snake in the world is the cobra (ko'bra) 
of India, where thousands of the natives die annually from 
its bite. 

Snakes swallow their food whole, and as the teeth are 
used merely for holding their prey, they point backwards. 



Figure 88. — Garter Snake — Harmless. 


Fear of Snakes. — In the case of many grown-up people 
there is a senseless fear of even the smallest snake. Small 
children are seldom afraid of snakes until some older person 
tells them that snakes are poisonous or that they will be 
bitten if they handle them. As a matter of fact the com¬ 
mon snakes of the garden will not bite when carefully handled 
but rather seem to like to be handled. When one stops to 
think that snakes are cold-blooded while the hands are warm 




SNAKES 


103 




it is not strange that they might come to enj oy the human 
hand. Some people are so frightened when they see a snake 
that a whole day of pleasure may be spoiled on this account. 


Figure 89. — Bull Snake with Hen’s Egg in Mouth. 

It is unwise to put fear where there should be none and it is 
unwise to imagine that a harmless snake will bite. Fear 
takes a toll of our nervous energy and if we can learn to 


Figure 90. — Bull Snake after Swallowing Egg. 

banish senseless fear we have done something towards pro¬ 
longing life and making our lives more efficient. 

We need to learn about snakes enough at least to tell the 







104 


REPTILES 


harmless ones from the poisonous ones. Also, we learn to 
overcome our fear of the little snakes. If one does not fear 
snakes and can handle them without minding, it is not wise 
to run after others with a snake in hand. People cannot 
be frightened out of their fears. A better way is to show 



Figure 91. — Alligator’s Nest. 

The heat of the decaying vegetation aids in hatching these eggs. Turtles 
lay their eggs in the sand. 


them by handling a snake gently that it will not bite and 
that it enjoys being handled. 

88. Alligators and Crocodiles. — Crocodiles are found in 
the Southern United States, South America, Africa, and 
India. Alligators are found in stagnant pools in the Southern 
States. Crocodiles resemble alligators but have narrower 
mouths. 

89. Adaptations. — Reptiles are peculiarly adapted to 
their environment. Snakes that live in trees are some- 




ADAPTA TIONS 


105 




Figure 92. — Eight-foot Florida Alligator. 

times the color of leaves or bark. Some that are harmless are 
colored much like poisonous snakes. An adaptive feature 
of the crocodile is a fold of skin which shuts off the mouth 
from the throat and prevents water from entering the 
throat while the crocodile is drowning its prey. The old 
world chameleons have their feet modified for clasping 


Figure 93. — Poisonous Lizards — The Gila Monster. 
Native of Mexico. 




106 


REPTILES 


branches. In the case of the turtles, those that live in 
the sea have paddle-like feet for swimming, while those 
that live partly on land and partly in the water have toes 
with webs. Lizards are almost always of about the same 
color as their surroundings. 


SUMMARY 

The reptiles always use lungs for breathing. They 
usually have scales or bony plates in the skin and have 
either two pairs of appendages (turtles, lizards, alligators, 
crocodiles) or none (snakes). It is important to learn to 
recognize poisonous reptiles, as their bite is dangerous. 

LABORATORY QUESTIONS 

From models or preserved specimens the difference between the harm¬ 
ful and harmless reptiles should be worked out. The living turtle can be 
studied easily. Its special skeleton is an illustration of protective 
adaptation. Notice how the nostrils of the aquatic turtle can be closed. 
How does this help the turtle? 

QUESTIONS 

What are the most common snakes in your vicinity? Are they 
poisonous? How can you tell? Where do they live? What do they 
eat? How many kinds of turtles do you know? Where do they live? 

REFERENCES 

Ditmars, The Reptile Book. 

Jordan, Kellogg and Heath, Animal Studies. 

Linville and Kelly, General Zoology. 

Reese, The Alligator and its Allies. 

Reese, Alligators as Food. 


CHAPTER VII 


BIRDS 


90. Bird Characteristics. — The front legs of birds are 
modified into wings. Among some birds, like the penguins 
(pen'gwinz) of the Antarctic region, the wings are not used 



for flying but to assist in swimming. In others, like the 
eagles and condors, the expanse of the wings is sufficient to 
enable them to fly away with young lambs and large fish. 
Between the small wings of the penguin and the expanse of 
the wings of the eagle and condor there are many variations. 

Bird wings are adapted to the needs of their owners. 

107 





108 


BIRDS 



Sailing birds, like the gulls, have long, slender wings, while 
ground birds, like the partridge and pheasant, have short 
wings capable of rapid, short flights. Those birds that make 
the most use of wings have them best developed. An 
example of underdevelopment, which has been increased by 
domestication, is seen in the domestic fowl, a ground bird, 


Figure 95. — Herring Gulls. 

Note the different position and shape of the wings. 

which makes little use of its flying powers, and is incapable 
of sustained flight. 

The legs of birds also have many variations. In the case 
of the eagles, hawks, and owls there are powerful claws for 
seizing and holding prey, while ducks and geese have long 
and webbed toes, adapted to swimming. Seed-eating birds 
have weak claws which serve merely for perching. Chimney 
swifts, that spend most of their time in flight searching for 
food, have well developed wings, and feet used for clinging. 
Study Figures 96 and 97. 





BIRD CHARACTERISTICS 


109 


The beaks of birds show great variation and adaptation 
for defense and food-getting. Hawks, owls, and eagles 
have the upper jaw curved over, hooked, and adapted for 
tearing their food; herons and bitterns have the beak modi¬ 
fied into a long, pointed weapon of offense and defense; 
grosbeaks (gros'beks) and finches have a short, stout beak 
for crushing seeds and other hard foods; while humming 
birds have a long, slender 
beak which in some kinds 
is curved so that they 
may reach the bottom of 
certain flowers. Study 
Figures 94, 99, 107, 109. 

The birds show a num¬ 
ber of other interesting 
adaptations which are of 
use to them. These are 
hollow bones, a keeled 
sternum (breastbone),and 
a high body tempera¬ 
ture. 

The skeleton of a bird 
shows a prominent ridge 
on the breastbone. This 
is the keel of the ster¬ 
num, which serves as a 
place of attachment for 
the large wing muscles 
(Figure 98). The lungs of the bird are small, but air tubes 
extend into the bones, so that the body of the bird is 
relatively lighter than that of animals with solid bones. 

Birds lead an active life, which means that they use a 
great deal of energy. This energy comes from the oxidation 
going on in the body. In birds, oxidation is more rapid than 
in other vertebrates, owing to the fact that they almost 






110 


BIRDS 


completely change the air with each breathing movement and 
thus secure a greater supply of oxygen. The rapid oxidation 

requires that a large 
supply of food be di¬ 
gested and assimilated 
rapidly and it makes the 
normal body temperature 
of birds higher than that 
of other vertebrates. 

Plumage. — Birds are 
the only vertebrates hav¬ 
ing feathers and their 
plumage shows great 
variety in form and color. 
In some species there are 
certain colors which al¬ 
ways predominate on the 
males, while the females 
have little color; in other 
species it is hard to dis¬ 
tinguish between the sexes. The brilliantly colored males 
are supposed to attract the females at the mating season, 
while the dull colored females are inconspicuous and less 
likely to be attacked by enemies while 
hatching their eggs, or caring for their 
young. We may say, therefore, that they 
are protectively colored. The color of 
birds varies during the first two or three 
years of life. 

91. Classification. — Birds are usually 
divided into groups according to their 
structure. The shape and size of the beak 
and of the feet and wings are the charac¬ 
teristics most used in the general classifi¬ 
cation. This is illustrated by a single 



Figure 98. —Skele¬ 
ton of a Mallard 
Duck. 



A , Ostrich’s foot — adapted for running; 

B, duck’s foot — adapted for swimming; 

C, hen’s foot — adapted for scratching; 

D, plover’s foot — adapted for wading; 

E , hawk’s foot — adapted for tearing ; 

F, crow’s foot — adapted for perching ; G, 
woodpecker’s foot — adapted for climbing. 











John James Audubon (1780-1851), self-trained naturalist, sup¬ 
ported his family by drawing portraits. His father was a French 
naval officer and his mother partly Spanish. He spent a few years 
in France where he gave his main energy to music, drawing, and 
natural history during the period when he was in' training for the 
navy. 

After his return to America about 1800, he became a wandering 
naturalist, ever seeking for new birds to study. As he went from 
place to place, he would pay for his lodgings or a new pair of 
shoes by making a portrait of some local celebrity or even the 
shoemaker himself. 

His most famous work consists of one-thousand and sixty-five 
natural sized, colored figures of American birds, the publication 
of which alone took ten years and cost $100,000 Whenever you 
visit a large library, ask to be shown Audubon s Birds, the most 
noted book on American birds. 




/ 





CLASSIFICA TION 


111 



group of birds, the hawks, owls, and vultures, which are 
given the technical name of Raptores (rap-to'rez: Latin, 
rapere, to ravish), birds of prey. The bird books describe 
the Raptores as follows: toes four, three in front and one 
behind, except in the vultures; all toes armed with strong, 
sharp, curved talons (tal'unz); bill with a cere (ser: Latin, 


Figure 99. — Head of Young Eagle. 

Notice the curved beak for tearing. 

sera, wax) or covering of skin at its base through which 
the nostrils open, very stout and strong, the upper mandible 
tipped with a sharp pointed hook. 

In addition to this classification by structure, which is 
essential for a careful study of birds, they are also classi¬ 
fied by their habits. For example, birds are divided into 
four classes based on their migratory habits. Birds like 
the downy woodpecker and English sparrow are permanent 
residents throughout their range, that is, they can be found 
within given limits at any time of year, while bobolinks 



112 


BIRDS 


and humming birds are summer residents, migrating south¬ 
ward at the end of the season. Birds like wild geese, fox 
sparrows, and the like, are transients, stopping along their 
migratory route for rest or food or to escape unfavorable 
weather; while such birds as the snowy owl, northern shrike, 
and evening grosbeak are winter visitants which migrate 



Figure 100 . — Loggerhead Shrike. 

This bird has. the habit of hanging in¬ 
sects and small birds on the long thorns 
about its nest as it usually kills more than 
it can eat. 


to us from the North 
when the cold becomes 
excessive and the food 
supply is diminished. 

Birds are classified also 
by their nesting habits. 
Some birds, like' the 
meadow lark and bobo¬ 
link, nest in the open 
field, and their nests are 
made inconspicuous 
rather than inaccessible; 
other birds, like certain 
hawks and eagles, build 
their nests in tall trees, 
making them conspicu¬ 
ous, but inaccessible. 
Still others build like the 
oriole at the end of slen¬ 
der branches where they 
are out of reach of ani¬ 
mals. Birds like the 
kingfisher, sand swallow, and puffins build their nests at 
the bottom of a burrow in the ground. 

92. Nest Building. — Birds show great variation in nest 
building. Some build a large nest with materials loosely 
put together; others build small nests of neatly woven 
material, and some birds, like cowbirds, build no nest at 
all, but lay their eggs in the nests of other birds and 



MIGRA TION 


113 


leave the work of caring for their young to the foster 
parents. 

The number of eggs that birds lay in their nests varies from 
one to as many as thirty or forty. The time required to 
hatch the eggs varies from ten days to six weeks. Birds 
whose eggs hatch in ten days or two weeks are called altricial 
(al-tri'shal: Latin, altrix, nurse), for such young are hatched 
helpless, blind, and with little down. Eggs that hatch in 
from three to six weeks develop well-formed young, able to 
run around within ten to twelve hours after hatching. These 
are known as prcecocial 
(pre-ko'shal: Latin, prae , 
before ; coquere, ripen). 

Such birds have little 
need for a substantial 
nest and few of them 
build one. The robin is 
altricial, and the domes¬ 
tic fowl prsecocial (Fig¬ 
ures 102 and 103). 

93. Migration. — Be¬ 
cause they are provided 
with wings and the power 
to fly long distances, birds 
are able to move from 
one region to another for the purpose of finding food 
and rearing young. The precise cause of migration is 
still unknown. Birds in general migrate to a warmer 
climate in the fall of the year and return to the cooler 
region in the springtime. In some cases birds cross the 
equator in migrating. For example, the bobolink nests in 
the Northern United States and passes the winder in South 
America, migrating a distance of over five thousand miles. 
In the case of the robin the migration is limited to a short 
flight to the South to some protected swamp provided with 



Figure 101 . — The Robin. 

Sometimes a permanent resident in 
the North. 





114 


BIRDS 



water and food. A probable cause of migration is the failure 
of food supply as cold weather comes on in the fall. 

94. Economic Importance of Birds. — The chief food of 
birds is insects, such as plant lice, larvae of beetles, butterflies, 


Figure 102 . — Young and Adult Chestnut-sided Warbler. 

moths, borers, etc. The chickadee, for example, feeds on 
plant lice as well as other foods; the downy woodpecker 
feeds on codjing moths and borers; the nuthatches and brown 
creepers feed on insects and insect eggs that are hidden in 
crevices and under loose pieces of bark. Other useful birds 
are the song-sparrow, chipping-sparrow, robin, bluebird, 





ECONOMIC IMPORTANCE OF BIRDS 


115 


wren, blackbird, etc., which feed principally on insects 
that are found on or near the ground. The insects that 
fly, like mosquitoes, gnats, and house-flies, are eaten by 
swifts, swallows, night-hawks, kingbirds, and fly-catchers. 

Among the hawks and owls is found a long list of bene¬ 
ficial birds, for the screech owl, red-tailed hawk, and the red¬ 
shouldered hawk are almost without exception valuable as 



Figure 103 . — Eggs of the Woodcock. 


The nest is merely a depression in the leaves with no lining. The young 
leave the nest within a few hours after hatching, so that a nest to hold the 
young would be useless. Young that leave the nest soon after hatching are 
called praecocial. 


destroyers of shrews, moles, mice, rats, weasels, and rabbits. 
The hawks that are partly harmful are the sharp-shinned 
hawk, Cooper’s-hawk, and the marsh-hawk. All these help 
themselves to poultry and feed on small beneficial birds 
like the song-sparrow and bluebird. 

The exact relation of birds to agriculture and the foods that 
they eat has been a subject of study by the Department of 




116 


BIRDS 


Agriculture. Fisher re¬ 
ports the following re¬ 
sults in his analysis of the 
stomach contents of 220 
red-shouldered hawks: 3 
contained poultry; 12 

held 102 mice; 40, other 
mammals ; 20, reptiles ; 
39, amphibians; 92, in¬ 
sects ; and 16, spiders. 
A similar analysis of 133 
stomachs of Cooper’s- 
hawks shows the follow¬ 
ing : 34 of the stomachs 
contained poultry or game birds ; 52, other birds ; 11, mam¬ 
mals ; 1, a frog; 3, lizards; 2, insects, while 39 were empty. 

Aside from being of value in the destruction of insects, 
birds destroy waste matter and dead animals lying on the 
ground. The vultures 
and buzzards of the South 
and West eat dead ani¬ 
mals. The gulls of the 
sea and lakes destroy 
refuse thrown upon the 
surface of the water. 

The eagle is also a scaven¬ 
ger, as it eats dead fish 
that float on the surface 
of the water, or small 
dead animals lying in the 
open on the land. Crows 
also eat dead fish. 

There is a group of 
birds that [lives largely 
on seed, and such birds 




Figure 104 . —Junco. 


A transient bird nesting in Canada and 
on the high hills and mountains of the 
Northern States. Beak is adapted for 
breaking small seeds. 





METHODS OF ATTRACTING BIRDS 


117 


destroy vast amounts of weed 
seeds. Among the seed 
eaters are the quail, grouse, 
pheasant, goldfinch, spar¬ 
row, bobolink, and meadow 
lark. A definite plan for bird 
study is suggested in the 
appendix. There are many 
facts which we should know 
about each bird which are 
more important than know¬ 
ing its name. 

95. Methods of Attracting 
Birds. — For the purpose of 
study and of appreciation, it 
is advantageous to bring the 
birds near the windows of a home where we may look upon 
them at odd times and study them at close range. There 
are several ways of getting the birds to come near a building. 
A common method is by feeding them. Foods such as suet, 
bread crumbs, hemp, canary seed, sunflower seeds, and raisins 
are attractive to birds. They should be so placed that cats 

cannot strike down the 
birds while they are feed¬ 
ing. Unless some care is 
exercised in selecting these 
feeding places, the birds 
will be lured into the claws 
of the ever waiting cat. 

Suet may be placed on 
the side of a tree trunk 
three or four feet from the 
ground in a bag or in a 
hole bored in the tree. 
Bird seed and crumbs may 



Figure 107 . — Kingfisher. 

What advantage does a long sharp 
pointed beak give this bird? Note the 
short legs and small toes. Do king¬ 
fishers use their feet in catching fish ? 



Figure 106 . — Female Bobolink:. 


Notice the short, stout beak. This 
bird feeds on seeds during a part of 
the year. How would such a beak 
be an advantage ? 





118 


BIRDS 



be placed on the ground, but a better method is to put the 
seeds and crumbs in a box, with a cover a few inches above 
to keep out the snow. This box should be placed on a post 
or on the side of a tree trunk a few feet from the ground. 
Food placed on the ground is apt to be eaten by stray dogs 
or cats and in the winter time it will be buried by the snow. 


Figure 108 . — Young Crows in Nest Waiting for Food. 

Sunflower heads may be hung to the sides of a tree trunk or 
put on the end of a post. 

During the winter the chickadee, whitebreasted nuthatch, 
downy woodpecker, hairy woodpecker, red-headed wood¬ 
pecker, brown creeper, flicker, and many other birds may 
come to the suet. Juncos, tree-sparrows, house-sparrows, 
pheasants, crossbills, evening grosbeaks, song-sparrows, and 
prairie horned larks will come to the bird seed and crumbs. 




NESTING BOXES 


119 



Sunflower seeds will attract chickadees, house-sparrows, 
crossbills, goldfinches, and evening grosbeaks. 

96. Nesting Boxes. — The putting up of nesting boxes 
in the yards is another way of attracting birds. In locating 
these nesting boxes it is essential to success that the place 
selected should be safe from cats. Cats will climb to the 
boxes if they can and strike the birds as they leave the nest. 
When birds are given a 
choice between several 
boxes put up in a small 
area, they seem to select 
those that afford them 
the best protection from 
their enemies. Boxe s put 
up on the ends of posts 
and away from trees seem 
to be preferred to those 
put up in the trees. Poles 
and posts may be covered 
with tin or sheet iron to 
keep the cat from climb¬ 
ing them. The size of 
the opening and the in¬ 
side space determine what 
birds will be likely to use 
the boxes. The table at 
the end of this chapter (see page 124) will give an idea of 
the size of the opening and the cavity and locations that 
are considered proper for some of our town birds. 

97. Bird Baths. — During the dry weather of July and 
August, the supply of water is greatly reduced. Sometimes 
the water that is available is in a place where the birds have 
no chance of escaping a cat that is lying in wait for them. A 
shallow plate of water placed on a stump or post in the shade 
is frequently used by the birds. Sometimes a dozen or more 


Figure 109 . — Hairy Woodpecker 
Eating Suet. 

Note the long, stout beak, the toe nails, 
and the tail used as a prop. How are each 
of these useful to the woodpecker ? 



120 


BIRDS 



Figure 110 . — Male and Female Cowbirds. 

Notice the difference in shade of the two birds. The female at the right 
is gray. What advantage would a dull color be to her while she was in the 
nest of another bird ? 

kinds of birds will come to these drinking places. At one 
such bath the following birds came during one summer: 
robin, oriole, catbird, yellow warbler, song-sparrow, pewee 
(to catch insects at the water), red-headed woodpecker, black- 
throated blue warbler, and goldfinch. Birds will bathe in 
the drinking fountains if they are shallow enough to allow 
them to wade. 

98. Adaptations of Birds for Winter. — Birds have several 
ways of meeting the unfavorable conditions of winter. 
The great majority migrate to a more favorable climate, the 
bluebirds going to the Southern States, while the bobolinks 
migrate to South America, some of them as far as Argentina. 
The red-headed woodpecker lays up beechnuts and acorns in 
the fall and feeds on them during the winter. The gold¬ 
finches that are common about our homes in the early fall 
gather in flocks and frequent swamps and heavy timbered 
regions, feeding on fruits that still cling to the trees. The 
ruffed grouse has a fringe of tissue that grows on its toes 







ADAPTATIONS OF BIRDS FOR FOOD-GETTING 121 


which act as snow shoes, enabling it to run over the snow 
without sinking in. This adaptation disappears in the spring 
when the need for it no longer exists. In the case of the 
ptarmigan of the Western States, the winter plumage is white 
but the summer plumage is brown and gray. The white 
plumage matches the snow, making it more difficult for 
enemies to find the bird, and the white plumage is warmer 
than any other color. 

99. Adaptations of Birds for Food-getting. — These adapta¬ 
tions are chiefly seen in the beak and the feet. The hooked 
beak of the eagle is an adaptation for seizing and tearing. 
The long beak of the kingfisher is an adaptation for spearing 
fish. The beak of the cowbird is short and thick for breaking 
up seeds. The hairy woodpecker has a chisel-like beak for 
cutting holes in trees, where it finds its food. The woodcock 
has a flexible beak for probing in the mud (Figure 111). 

The strong feet and curled claws of the hawk are adapta¬ 
tions for seizing and holding its prey. The long toes of the 
gallinules allow them to walk over floating leaves in search 
of food. The woodpeckers have two toes in front and 
two behind which give them a firm hold on the bark while 
they are driving holes in the tree. The loons have webbed 
toes that they may swim under water and pursue fish. The 
domestic fowl has large strong nails to assist in scratching 
for its food. The beaks and claws of most birds will be 
found fitted for the kind of work that the birds must do, 
either to procure food or to protect themselves. 

100. Public Museums. — As man came to occupy the 
land, the forests were cleared away and the ground used 
to produce food for man and domestic animals. This 
tended to drive the wild life, native to such regions, into 
the mountain fastnesses where they were free to live. 
This resulted in many of them becoming extinct even when 
they were of great use to man. The bison and brook-trout 
are two good examples (Figure 61). The expense of collect- 


122 


BIRDS 



Figure 111 . — Woodcock on Nest (incubating). 

This is an example of protective coloration. The pattern of the sitting 
bird blends with the surroundings soThat-it is difficult to see the bird as long 
as she remains quiet. Note that this bird can see directly behind her with¬ 
out turning her head. The eyes are placed well back in the head. This is 
an adaptive feature and serves to protect her. 

ing and properly housing the preserved skins and skeletons 
of such animals is beyond the means of most people. The 
public museum is the proper place for all such collections, 
as a few specimens which can be seen by all is much better 
than many specimens in private collections. The men in 
charge of museums never indulge in useless slaughter as is 
so frequently done by hunters. 



PUBLIC MUSEUMS 


123 



Every student in such a course as this should plan to visit 
the public museum or zoological park or botanical garden in 


his city as the different 
parts of the course are 
taken up. Pictures and 
drawings can never take 
the place of seeing the 
actual specimens. Going 
to the museum is like 
going into the laboratory 
for first-hand study of 
the facts. It is studying 
nature as she is. 

101. Public Preserves. 
— During the past few 
years, large areas have 
been set aside where the 
wild life, especially the 
birds, can live unmolested. 
Many bird refuges are 
being established over the 
country where no one is 
allowed to hunt birds. 
In these refuges (or pre¬ 
serves) nesting boxes are 
put out for the birds to 
use, drinking fountains 
are kept running during 
the dry seasons, and food 
plants for birds are set 
out or the seed sown. 


Figure 112. —Nest of the Yellow 
Warbler in which a Cowbird Egg 
Has Been Laid. 

The warbler first built the nest at the 
bottom. When this nest received a cow- 
bird egg, a second nest was built on top. 
Again it was visited by a cowbird and a, 
third nest was made. When the cowbird 
egg hatches, the young is larger and 
grows faster than the small warblers. 
After a time this large bird crowds the 
small warblers out of the nest and they 
die. What should you do when you find 
an egg of a cowbird in a warbler’s nest ? 
From Zoological Museum, University 
of Minnesota. 


Many farmers post their 

lands in order to save the game birds and game animals 
that are in danger of being exterminated by too much 
hunting. 






124 


BIRDS 


SUMMARY 

Because of their feathers birds can easily be recognized. 
The fore-limbs are adapted for flying, and as such vary in 
size. The feet are modified for swimming, running, perch¬ 
ing, or tearing; while the jaws are large and powerful, or 
small and weak, depending on the habits of the bird. The 
classification of birds according to their habits makes it 
easy to learn about them. Birds are of great economic 
importance in destroying many kinds of insects that are 
detrimental to man. This explains why they must be pro¬ 
tected by law. 

TABLE —SIZE OF NESTING BOXES 


Bird 

Diameter of 
Opening 

Size of 
Cavity 

Location 

Chickadee. 

11 n 

1 8 

4X4 

In protected spots 

House wren. 

11 " 

X 8 

4X4 

Trees and arbors 

Nuthatch. 

11 " 

1 4 

5X6 

On buildings or trees 

Bluebird. 

11 " 

1 4 

5X6 

On buildings or trees 

Tree-swallows .... 

11 // 

J-4 

5X6 

In trees near ponds 

Red-headed woodpecker 

2i" 

6X7 

On posts or trees 

Flicker. 

3" 

6X8 

On posts or trees 

Wood-duck. 

6" 

10 X 18 

Trees or stumps 


QUESTIONS 

How many birds do you know? What do they eat? Do they 
remain all winter ? Which ones migrate ? Where do they nest ? What 
time of year do the young leave the nest? Why are the birds bene¬ 
ficial ? 

REFERENCES 

W. L. McAter, How to Attract Birds in Northeastern United States. 
Farmers’ Bulletin 621. 

Chapman, Bird Life. 














CHAPTER VIII 


MAMMALS 



102. The Mammals are the most highly developed of the 
vertebrates. They are warm blooded (the body tempera¬ 
ture remaining the same in winter and summer), breathe 
by means of lungs, and 
are provided with milk 
glands to nourish their 
young. Most mammals 


Figure 113. — Skeleton of 
* a Dog. 


Fi gure 114. — Coyote. 

These animals do many thousand dol¬ 
lars of damage annually to the breeders 
of cattle and sheep in the Western 
States. 


are covered with hair. A muscular wall (diaphragm) sub¬ 
divides the body cavity into two parts. The anterior part 
contains the heart and lungs, and the posterior part con¬ 
tains the stomach, intestines, liver, and other organs. At 
birth the young look like the parents. 

Most mammals have two pairs of limbs. The fore limbs 
may be variously modified for different uses, as for walk¬ 
ing in animals like the horse, for climbing and for food- 

125 







126 


MAMMALS 



getting in the squirrel, for burrowing and locomotion in the 
moles, for flying in the bats, and for swimming in the seals. 
In all fore-limbs of mammals, even in those as different as 
the leg of the squirrel, the flipper of the seal, and the wing 

of the bat, the arrange¬ 
ment of the bones is the 
same. The hind-legs of 
mammals do not show 
so much variation as the 
fore-limbs. But in some 
cases, as in the whale, 
the hind-legs have almost 
disappeared through dis¬ 
use, and there is no ex¬ 
ternal evidence of them. 
Some animals, like the 
bears, walk on the soles 
of their feet, and some, 
like the cats and the 
dogs, walk on all their 
toes. In some mammals 
there is a variation in the 
number of the toes. For 
example, the cow walks 
on two toes and the horse 
on one toe, the hoof being 
a modified toe nail. In 
such cases the other toes 
are entirely lacking or rudimentary (not perfectly developed). 


Figure 115 . — Flying Squirrel. 

The skin is stretched between the fore- 
and hind-legs and acts like a parachute. 
Does the animal really fly ? 


103. The Horse. — The horse is interesting because it has 
been associated with man since the pre-historic period known 
as the Stone Age. It has been suggested that man “ first 
hunted horses for food, then drove them, and finally used 
them for riding and as beasts of burden.” The fine animals 
which we see to-day have gradually developed through this 



THE HORSE 


127 



Figure 116. — Brown Bat. 


Notice how the wings of the bat are formed. Membranes are stretched 
between the bones of the fingers, between the arms and legs, and between 
the legs and tail. This entire structure is known as the wing of the bat. 
How does it differ from the wing of a bird ? What other special adaptations 
do you see ? 



Figure 117. — Bat Hibernating. 


During the winter sleep the bat hangs 
suspended in some cave. 







128 


MAMMALS 



long time from a small animal about the size of a fox terrier. 
The earliest remains of the feet of the ancient horse show 
that it had four toes and the remains of a fifth in the front 
foot, while the hind foot had three toes and the remains of 
a fourth. The horse and the deer, which also has many 


Figure 118. — An International Champion Draft Horse of the 
Percheron Breed. 

Compare the size of the neck, shoulders, and hips with the same parts of the 
trotter breed in Figure 119. What kind of work can this horse do best? 

stages preserved in the rocks, afford examples of the manner 
in which some of our present animals have developed. 

The domesticated horses were developed in the old world. 
In the warmer regions, where food was plentiful, the larg¬ 
est horses developed, while in the north, where food was 
less abundant and the conditions were more severe, the 
Shetland pony appeared. Most breeds of horses were de- 




THE HORSE 


129 



Figure 119. — A Standard Breed of Trotting Horse. 
Compare the various parts of this horse with the draft horse in Figure 118. 


veloped in France and England. There are three general 
types: namely, draft horses, which are the largest and 
heaviest, with short, strong limbs and thick necks, of which 
the Percheron, Belgian, and Clydesdale are common types; 
coach or carriage horses, which are graceful and plump but 
not so heavy as the draft 
horses; and roadsters or 
trotting horses, which are 
the lightest and slimmest 
of the horses. Roadsters 
have long legs, a thin 
neck, and are noted for 
their intelligence. Saddle 
horses belong in this third 
class (Figure 119 a fine 
specimen). 

The mule has been Figure 120. —Deer Mouse. 

known for many cen- a nocturnal rodent. A flashlight photo- 
turies. Even in the days graph. 







130 


MAMMALS 


of ancient Greece and Rome mules were used in agriculture. 
They are stronger, more patient, live longer, and are surer 
footed than horses. Because of their great endurance and 
adaptability, they are more widely used than horses. 

104. The Cow. — Cattle are descended from the wild ox 
of Europe and Asia, and practically all our popular breeds 



Figure 121.— Holstein Cow and Calf. 

This cow gave 653 pounds of milk in seven days and 101 pounds in 
one day. The 653 pounds of milk yielded a little over thirty-three pounds 
of butter. This is one of the highest records ever made. The Holstein 
breed of cows is also as good for beef as they are large. 

have been developed in Europe, mainly in the British Isles. 
There are two main types of cattle: the beef type used for 
food and the dairy type most valuable for the milk, butter, 
and cheese that they produce. The beef type is character¬ 
ized by “ blocky ” bodies, a form which yields the greatest 
quantity of meat. The beef cow is not expected to produce 
much milk. Shorthorns and Herefords, English breeds, 
also Angus and Galloway, Scotch breeds, are good repre- 




THE COW 


131 


sentatives (Figure 122). The dairy type presents a dif¬ 
ferent appearance from the beef type, having much less 
regular bodies and very large udders. The Island breeds, 
Jersey and Guernsey, are among those most famous for the 
production of butter fat rather than for the quantity of 
milk. Jerseys are especially valuable as family cows. 



Figure 122. — A Prize Hereford Bull that Sold for $15,000. 
The Herefords are a breed of cattle especially raised for beef. Why ? 


Guernseys, larger and heavier than Jerseys, yield more 
milk and more meat. The Ayrshires, a Scotch breed, are 
known for the superiority of their milk for cheese, for the 
large proportion of butter fat, and for the fact that they 
yield more beef than any other dairy breed. Dutch cattle, 
the Holstein-Friesian breed, are famous for the quantity 
of milk that they produce. The milk is superior for cheese¬ 
making and, on account of the large quantity they produce, 
these cattle rank foremost in supplying cities with milk. 






132 


MAMMALS 



Oxen of this breed grow to large size and are much prized as 
work animals (Figure 121). 

105. Sheep. — Sheep have been domesticated for ages, 
being possibly the first mammals domesticated by man. 
They thrive in nearly all climates and can find food where 
other mammals can scarcely live. Sheep furnish wool and 
meat. There are three classes, based on the quality of the 


Figure 123. — Two Yearling Ewes and Two Ewe Lambs. 

The famous Hampshire breed of coarse wool sheep. Compare with 
Figure 124. 

wool. These are the fine wool breeds like the Merino, 
which had its origin in Spain, whence they have been carried 
to all countries where sheep raising is an important industry ; 
the medium wool breeds like the Southdown; and the long 
wool breeds like the Leicester, both of which are English 
breeds. The fine wool breed is raised principally for the 
wool, the meat value being a secondary consideration. The 
medium wool breeds are raised principally for the meat and 




PIGS 


133 


wool is a secondary consideration; while in the long wool 
breeds the mutton and the wool are of equal importance. 
Closely related to the sheep are the goats, which are the 
main dependence for milk and meat in the Island of Malta, 
Switzerland, and Asia Minor. 


106. Pigs. — The pig has been developed from the wild 
boar of the old world. Meat is obtained more cheaply 
from the pig than from any other animal, because it adds 



Figure 124. — A Group of Rambouillet Sheep. 

These are the most famous of the fine wool breeds of sheep. They yield a 
large fleece of wool and are valuable as mutton. Compare with Figure 123. 


more weight for a certain amount of food than either sheep 
or cattle and does it in a shorter time. There are two 
types in our markets, the lard type and the bacon type, 
which are produced largely through the methods of feeding. 
The well-known Berkshires, an English breed, whose color 
is black, are regarded by many as the aristocrats among 
pigs. America is famous for the breeds of pigs developed 
here, of which the Poland-China, originating in Ohio, the 
Chester White, first produced in Chester County, Penn¬ 
sylvania, and the Duroc-Jerseys, of New Jersey, are among 
the most popular. 




134 


MAMMALS . 


107. Economic Importance of Mammals. — In his rela¬ 
tions with the organisms about him, man finds some helpful, 
some harmful, and some neither. As we have seen, the 
domesticated mammals, especially the horse, cow, sheep, 
goat, and pig, are of the greatest use to man in this part of 
the world. In cold regions, reindeer are the main de¬ 
pendence for food, clothing, and for beasts of burden. In 
desert regions, the camel is the most useful and in hot regions 
elephants are of great value as beasts of burden. Dogs and 



Figure 125. — Berkshire Pig-Mother and Family. 
This is one of the famous American breeds of pigs. 


cats have long been man’s companions. Of the wild mam¬ 
mals, seals and walruses, which live in the water, furnish 
food, fur, and leather. The whale furnishes whalebone, food, 
and oil. 

Man is learning to make use of the habits of other mam¬ 
mals ; for example, we build roosts in the vicinity of 
swamps and marshes to furnish shelter for bats by day. 
At night the bats fly about catching the insects which annoy 
man and his animals. There are harmful mammals, too, 
such as gophers (go'ferz), prairie dogs, and rabbits, which 






ECONOMIC IMPORTANCE OF MAMMALS 135 


injure man’s land and his crops. Rats and mice consume 
much food and destroy much that they do not eat, besides 
carrying diseases. Red 
houses, where they dam¬ 
age beds and furniture, 
and out of doors they 
destroy the eggs and 
young of birds. 

Rats , 1 mice, and guinea 
pigs have proved of great 
use in laboratories where 
the causes and effects 
of diseases are studied. 

Their reaction to diph¬ 
theria, tuberculosis, can¬ 
cer, and other diseases is 
similar to that of man. 

As a result of these 
studies the skillful physi¬ 
cian is more successful in 
relieving the sufferings of 
man. 


Report on Mammals to be filled out first from general knowledge, 
later extended by trips to fields, woods, or parks. 


Kinds 

Where 
’ Found 

Food 

Kind of 
Food 

Life in 
Winter 

Life in 
Summer 

Beneficial 

Harmful 










1 The Brown Rat causes damage to cereals and grains estimated at 
more than $200,000,000 annually in the United States. Read “The 
Brown Rat in the United States/' by David Lantz. Bulletin No. 33, 
Biological Survey, United States Department of Agriculture. 


squirrels gnaw their way into 



Figure 126. — Camel. The Ship of 
the Desert. 


In making long trips across the desert, 
the camel is able to go without drinking. 
During these journeys, the hump grows 
smaller as the fat in it is used as food. 
This food is gradually changed until part 
of it becomes water. We might say that 
the fat in the camel’s hump is a special 
water reservoir. 




















136 


MAMMALS 



Figure 127. — Bison. 

These sturdy animals once roamed the plains in great numbers. If they 
had not been protected in park preserves, they would now be extinct. 



Figure 128. — A Beaver Dam. 
Describe how it is made. 










THE BEAVER 137 

Lions and tigers sometimes kill human beings. Weasels, 
skunks, and mink do harm by killing poultry. 

108. The Beaver. — The beaver is one of our most 
interesting mammals because of its social habits and archi¬ 
tectural ability. The demand for its fur and oil has led to 
its extermination in many parts of the country. In the 
Adirondacks they were trapped and hunted with such vigor 
that for a few years previous to 1905 none was to be found. 



Figure 129 . — Young Poplar Trees Cut Down by Beavers. 
Notice the top of the stump. 


In 1905 several pairs were obtained from Yellowstone Na¬ 
tional Park and liberated near the old beaver haunts in the 
Adirondacks, and at the same time laws were passed pro¬ 
tecting them. Now they are numerous throughout the 
Adirondacks wherever natural conditions are favorable. 
The beaver is frequently selected as an emblem of industry. 
Some of the interesting facts in connection with the life of 
the beaver follow. 

1. With their strong teeth they are able to cut down trees 
more than a foot in diameter. 




138 


MAMMALS 


2. They cut up the trees into lengths which they can 
handle in the water (Figure 129). 

3. If the trees are large and there is no water near, they 
dig canals leading back to the fallen tree. 

4. They build dams that are eight or ten feet high and 
twenty or thirty feet wide. These dams frequently raise 
the level of lakes so that the shore line is changed (Figure 128). 



Figure 130. — A Beaver House. 
What is it used for ? 


5. If the stream is large and the pressure on their dam 
becomes too great, they build a secondary dam below the 
first one, which provides slack water and thus protects the 
main dam. 

6. Their houses are built of mud and sticks on the margin 
of the ponds after the dam is finished. They live in these 
houses and enter them from below the surface of the water. 
The purpose of the dam is to provide a pond with deep water 
for their protection and use (Figure 128). 







SUMMARY 


139 



Beavers live in colonies and work industriously in building 
dams and houses. Some damage is done by their cutting 
trees and damming up streams. The great popular interest 
in beavers and their works more than outweighs the little 
harm they do. 


Figure 131. — Runways of Muskrat. 

As the water in the pond recedes, the muskrats dig canals that enable 
them to reach water from their lodges in the bank without going over land. 
How does this show adaptation in the behavior of these animals ? These 
canals are often mistaken for beaver runways. 

SUMMARY 

The animals which are called mammals are covered with 
hair and nourish their young with milk. There are nearly 
always two pairs of appendages that undergo much modi¬ 
fication, according to the habits of the animals. Our do¬ 
mestic animals which serve us in so many ways have grad¬ 
ually developed into their present form and usefulness. 
Man had to learn first how to use the fur and skin of wild 
animals, then how to improve the quality of the fur and skin 
by careful feeding and breeding of the domesticated animals. 





140 


MAMMALS 


FIELD SUGGESTIONS 

If you are where you can visit a zoological park it is an easy matter 
to learn how to distinguish the different mammals, a thing which every 
one should be able to do. There is another line of study which consists 
in selecting some one or two of the common mammals, such as squirrels, 
and making a thorough study of them from week to week, month to 
month, year after year, until you feel thoroughly acquainted with them. 
A third line of study is that of hibernation. Some mammals do not 
hibernate, some do so only during cold snaps, while others go to sleep 
for the entire winter. Consult, Walter B. Taylor, Suggestions for 
Field Studies of Mammalian Life-histories — United States Depart¬ 
ment of Agriculture, Department circular 59, 1919. 

QUESTIONS 

How do you tell a mammal from other vertebrates ? What mammals 
live near your home? What do they eat? Where do they spend the 
winter ? 

REFERENCES 

Davenport, Domestic Animals and Plants. 

Linville and Kelly, Zoology. 

Plumb, Types and Breeds of Farm Animals. 

Stone and Crane, American Animals. 


CHAPTER IX 


THE SIMPLEST ANIMALS — PROTOZOA 

109. Definitions. — In our study of the grasshopper and 
its insect relatives we considered their behavior and life 
processes. If we had studied the minute structure of any 
of these insects, the grasshopper, for example, and had used 
a microscope to aid us, we should have found that every 
organ was made up of numerous small parts joined together 
in a definite manner. These small parts are called cells. 

Any book on biology uses the word cell again and again. 
The name was first used by the Englishman, Robert Hooke, 
over two hundred years ago, when, with his crude micro¬ 
scope, he examined a piece of bark and found it to be made 
up of little rooms which looked like the cells of the honey¬ 
comb; These spaces he named cells. When better micro¬ 
scopes were made, the living parts of the cell were discovered, 
and it was found that Hooke had seen only the walls of dead 
cells. 

All plants and animals are composed of cells. A cell may 
exist alone, carrying on all the life processes itself, or it may 
exist in connection with a great many other cells, as in all 
large animals and plants. In every case each cell is pro¬ 
duced from another cell. 

There are certain animals that are never more than one- 
celled even when they are full grown. These animals are 
called Protozoa (pro-to-zo'a: Greek, protos, first; zoon, 
animal). 

110. The Protozoan Cell. — The protozoan cell is a single 
mass of living matter, called protoplasm. In a general way 
it carries on the same life processes as the grasshopper, or 

141 


142 THE SIMPLEST ANIMALS — PROTOZOA 

any other animal. When this living cell comes in contact 
with heat, cold, electricity, chemicals, or other stimuli, it 
moves, and we say that it is irritable. The term irritability, 
used with a scientific meaning, is defined as the power of 
being aware of a stimulus. When this living cell is brought 
into contact with cold, for example, it makes a definite 
movement. It is aware of the cold stimulus. 

The living cell grows by using food. It takes in oxygen 
from the water or from the air, according to where it happens 

to live. It gives off waste 
substances. It can grow 
and reproduce other cells 
of the same kind. 

Many protozoan cells 
have no limiting wall be¬ 
tween the living substance 
and the water in which 
they live. Yet the proto¬ 
plasm and the water do 
not mix, though we do not 
understand why. Other 
Protozoa living in the 
ocean are surrounded by 
extremely thin skeletons 
of lime. When the animals die their skeletons sink to the 
bottom and become massed in a sort of rock. The famous 
chalk cliffs of England were formed in this way. 

111. Habitat. — The habitat of any animal is the place 
where it lives. The Protozoa are small, usually micro¬ 
scopic, animals common in stagnant pools and in swamp 
water. They are also common in salt water. In fact, 
Protozoa are likely to be found in nearly all ponds of water 
that contain food for them. Often, in the summer time, 
our attention is called to the activities of Protozoa when 
the water from lakes or reservoirs has a fishy taste. This 





AMCEBA 


143 


peculiar taste may be due either to animals or plants, or to 
both. When it is due to animals, it is caused by a dis¬ 
agreeable oil formed by a certain kind of Protozoa. 

By far the greater number of Protozoa are harmless, 
and many are helpful to us in that they serve as food for 
fishes. Others, however, may become parasitic in our bodies, 
and thus cause such diseases as malaria, yellow fever, or 
sleeping sickness. 

112. Amoeba. 1 — The name Amoeba (a-me'ba) is given to 
several different Protozoa, but all represent the simplest 
form of animal life known 
to us. For this reason 
they are always studied in 
biology. In order to de¬ 
scribe correctly the struc¬ 
ture of even so simple an 
animal as the amoeba a few 
new words are necessary. 

Structure of Amoeba. — It is difficult for inexperienced 
students to see the living amoeba through the microscope, 
because the whole cell has a faint, grayish appearance, 
and in a strong light is transparent. But if this grayish 
appearance of protoplasm is once seen, it is always re¬ 
membered. 

There is no well-defined cell wall; therefore the amoeba 

1 No suggestion can be made which will always enable the teacher to 
secure amoebae. They are more frequently found in the slime and mud of 
stagnant water than anywhere else. Paramecia and other infusoria can 
usually be secured in abundance by placing a handful of hay or leaves in a 
jar and covering them with the ordinary water used in the laboratory. This 
is called a protozoan culture, and should be started about four weeks before 
the material is wanted for class study. The length of time that the culture 
should stand can be lessened by adding a little beef-extract and by keeping 
the jar near a radiator. Water sufficient to keep the hay or leaves covered 
must be added from time to time. When a good culture of Paramecia is 
once secured, the jar should be kept from year to year, simply adding water 
to the dried hay left in the jar when Protozoa are desired. 



Figure 133 . — Diagram of an Amceba. 








144 THE SIMPLEST ANIMALS — PROTOZOA 


is an illustration of a living, naked cell. Near the center 
of the cell is a spherical mass of denser protoplasm called 
the nucleus. In many amoebae the nucleus is not easily 
seen except by means of specially stained preparations. The 
rest of the protoplasm in the cell is called cytoplasm (sl'to- 
plazm). This does not appear the same in all parts of the 
amoeba. On the outside, there is a thin, almost transparent 
layer, called ectoplasm (ek'to-plazm: Greek, ecto, outside; 
plasma , form). The larger part of the cytoplasm is filled 
with numerous small granules and contains several vacuoles. 
This inner mass of cytoplasm is called endoplasm (en'do- 
plazm : Greek, endo, within ; plasma, form). The vacuoles 
in the endoplasm may contain food, water, or waste products. 
The food and water vacuoles are temporary structures, but 
the vacuole which collects the liquid waste is always present. 

The living amoeba is continually changing shape and 
pushing out from the surface of its body blunt, finger-like 
projections of the protoplasm called pseudopodia (su-do- 
po'di-a: Greek, pseudo, false; pod, root of pous, foot), 
which give an irregular outline to the body (Figure 132). 
Sometimes the pseudopodia branch out, and therefore the 
scientific name Rhizopoda (ri-zop'o-da: Greek, rhizos, root; 
pod, root of pous, foot) is the technical name for all amoeba¬ 
like Protozoa. 

113. Motion. — The amoeba sends out a pseudopodium, and 
gradually the rest of the body flows, by a rolling movement, 
in the same direction. This creeping-rolling motion of the 
protoplasm enables the amoeba to move through the water. 

114. Nutrition. — When the pseudopodium comes in con¬ 
tact with a minute plant upon which the amoeba feeds, the 
protoplasm of the pseudopodium surrounds the plant and 
takes it into the cell. The microscopic plant thus eaten 
by the amoeba is inclosed, with a small amount of water, 
in a tiny globe called the food vacuole (vak'a-ol). The food 
vacuole is to be thought of as a stomach in which digestion 


EXCRETION 


145 


can take place, for the plant is digested in it. Digestion is 
accomplished by means of an enzyme. The nutritious parts 
are absorbed into the protoplasm, the undigested parts are 
cast from the cell, and the food vacuole disappears. 

Food vacuoles are not always round (Figure 135), but take 
their shape from the form of the plant eaten. If a filament of 
alga, page 304, is taken as food, the food vacuole is much 
elongated. 

115 . Respiration. — From the air dissolved in the water, 
the amoeba obtains by osmosis the oxygen necessary to its 
life, and it gives off carbon dioxide from the cell. 

116 . Excretion. — The term, contractile vacuole, is given 
to the vacuole which is always present in the protoplasm of 
amoeba. This vacuole can be 
seen to increase slowly in size, 
then suddenly contract. As it 
contracts, the fluid in it is forced 
to the outside of the body of the 
amoeba. The filling out of this 
vacuole is due to the collection 
of excretory wastes from the sur¬ 
rounding protoplasm. It is called 
a contractile vacuole because it contracts and expands, and 
an excretory vacuole because it collects waste products. 

117 . Reproduction and Encystment. — The chief method 
of reproduction in the amoeba is simple (Figure 134). The 
living cell divides into two equal parts, forming two new cells. 
This process is known as fission (fishTin : Latin, fissus, cleft). 

When the food or water becomes unsuited to supply the 
needs of the cell, in order to live the amoeba often secretes 
(makes for itself) a thick wall completely surrounding the 
protoplasm. This process is termed encystment (en-sist'- 
ment: Greek, en, in; kystis, bladder). After the wall has 
been formed, the amoeba is able, for a long period, to resist 
cold, the drying up of the pond, or the lack of food. 



Figure 134. —Three Stages 
in Fission of Amceba. 




146 THE SIMPLEST ANIMALS — PROTOZOA 


118. Paramecium. — One of the most common forms of 
Protozoa is the slipper-shaped Paramecium (para-me'- 
shi-um), which is more active than the amoeba. It is 
abundant in stagnant water and in the hay infusions pre¬ 
pared in the laboratory. (See Laboratory Suggestions.) 

LABORATORY STUDY 

There are certain kinds of Protozoa that are usually found in pro¬ 
tozoan cultures. The most abundant form is the paramecium. Make 
repeated examinations of drops of water from the protozoan culture, 

until you are able to find the 
paramecium. Notice its 
shape, rate of movement, be¬ 
havior on meeting obstacles, 
and the like. Report on what 
you can make out. Compare 
the paramecium with any 
other protozoon you can find, 
as to shape, rate of movement, 
size, color, etc. If available, 
examine slides which show the 
nucleus of a protozoon. Make 
sketches that illustrate the 
above features. 

Structure of Parame¬ 
cium .—The paramecium, 
like the amoeba, is a single 
cell, but it has both a large nucleus and a small one. It 
has an endoplasm, an ectoplasm, and a cuticle (ku'ti-kl), or 
cell wall. Through the cuticle there extend great numbers 
of cilia (sil'i-a), or threads of living protoplasm. The ecto¬ 
plasm contains many thread-like darts known as trichocysts 
(trik'o-sists). These can be discharged. Within the cell are 
found food and water vacuoles as in the amoeba; but there 
are two contractile vacuoles, one at either end, and the 
food and water vacuoles are more numerous than in amoeba. 

119. Locomotion and Defense. — The, animal moves by 








NUTRITION 


147 


the action of the 
cilia, the direc¬ 
tion being due 
to the angle at 
which the cilia 
are held. It can 
be observed that 
the animals move 
backward and 
forward, and that 
they also rotate 
on the long axis. 

Paramecia de¬ 
fend themselves 
by discharging 
their trichocysts. 

This discharge 
occurs either as a result of certain strong artificial stimuli, 
such as electric currents or chemicals, or naturally because of 
collision with certain other Protozoa. If attacked by some 

animal which feeds upon 
them, they discharge the 
trichocysts in the region 
of the attack (Figure 
136). 

120. Nutrition. — The 

paramecium, like all 
other living things, re¬ 
quires food, which con¬ 
sists mostly of bacteria. 
These are collected by 
means of the cilia located 
on each side of the fold or 
depression called the 
gullet. At the inner end 


' * % - 
% , 5* - 

v y/" \f i 

** f • 

- $ * * ;■ 


Figure 137 . — Paramecium Stained to 
Show the Nucleus (Photomicrograph). 



Figure 136 . — Paramecium. 

Being attacked by another protozoon that fe'eds 
upon it. The trichocysts are discharged, and they 
force the foe away. 










148 THE SIMPLEST ANIMALS — PROTOZOA 


of the gullet is the mouth (Figure 135). The food thus col¬ 
lected passes into the protoplasm in the form of food vacuoles. 

Digestion is accomplished by the aid of 
enzymes which put into solution the avail¬ 
able parts of the food it eats, and the indi¬ 
gestible parts are cast off from the body. 

121. Respiration. —-As in amoebae, the 
Figure 138 . — Para- , . , . , . 

mecium Reproduc- ox yg en which is necessary to respiration 

ing by Fission. is obtained directly from the water and 
Compare the shape passes into the protoplasm at all points, 
of the nucleus with the 122. Excretion. — Excretory wastes are 
first collected in each of the two contrac¬ 
tile vacuoles and then cast from the body. Gases escape 
from the entire surface. 

123. Irritability. — Both the amoeba and paramecium re¬ 
spond to jars, food, and 
their enemies in a definite 
manner. In each of these 
simple cells there is no 
structure which can be 
compared to the nerve 
cells or brain of higher 
animals. The ability to 
respond to stimuli in Pro¬ 
tozoa seems to be a condi¬ 
tion that is present in the 
whole protoplasm of the 
cell. 

124. Reproduction.— 

Paramecia reproduce by 
fission, i.e. an animal di¬ 
vides, producing two ; 
these divide and produce two more. The process of fission goes 
on indefinitely (Figure 138). Unlike the amoeba these forms 
cannot encyst when conditions of life become unfavorable. 



This protozoon is supported on a stalk 
which can contract and expand. Of what 
use would this be ? 









OTHER PROTOZOA 


149 


125. Economic Importance. — Paramecia consume con¬ 
siderable quantities of bacteria, but whether more harmful 
than helpful ones cannot be told. Therefore their eco¬ 
nomic value is uncertain. 

126. Other Protozoa. — If one examines stagnant water, 
a large number of other kinds of Protozoa will be found. 
The more common forms are much like the paramecium 
and have many cilia on the body. Several of these large, 
ciliated Protozoa feed on the smaller Protozoa. Some of 
the common forms are shown in Figures 139-141. 


Figure 140 . — One of the 
Foraminifera. 



Figure 141 . — Some Flagellate Pro¬ 
tozoa. 


All these various Protozoa can be grouped into classes, 
each with certain distinct characteristics. For instance, all 
Protozoa that have pseudopodia are called Rhizopoda. In 
this group, the cells may be naked or may possess a hard 
mineral covering \ a second group of Protozoa are provided 
with one or more long, wavering threads called flagella 
(fla-jel'la: Latin, flagellum , whip), and have the name 
Flagellata; the flagella are longer than cilia and exhibit 
more complicated movement. A third class, known as 
Infusoria (in-fu-so'ri-a), includes most of the common Pro¬ 
tozoa found in protozoan cultures. Most of this class are 
provided with cilia. 






150 THE SIMPLEST ANIMALS — PROTOZOA 


LABORATORY STUDY OF PROTOZOA 

Take a drop of water from an infusion rich in Protozoa; place on a 
slide and examine with a 16 mm. or f objective. Answer the questions 
suggested by the report. 


Number of 
Kinds 
Observed 

How Many Kinds — 

How Many Kinds 
Have — 

are free 
swimming ? 

are 

attached 
by threads ? 

have even 
motion ? 

have zigzag 
motion ? 

constant 
form ? 

varying 
forms ? 









127. Protozoa and Alcohol. — Scientists have studied the 
relation of alcohol to the life processes of Protozoa. Nor¬ 
mally, such Protozoa as Paramecia divide a regular number 
of times each day. When a small amount of alcohol is 
placed in water containing Paramecia, the normal rate of 
fission is diminished. Professor Woodruff has shown by an 
extended and critical study that alcohol tends to prevent 
Paramecia from dividing as many times as they would under 
normal conditions. This means that alcohol hinders the 
growth of Paramecia. 

SUMMARY 

Protozoa are the simplest group of animals. They are 
found mostly in water, yet some are parasitic in higher 
animals. They are small and usually consist of only one 
cell. They reproduce mostly by fission. Some produce 
diseases in man and beast, such as malaria and the sleeping 
sickness of Africa. But the great majority of Protozoa are 
not harmful. 





















REFERENCES 


151 


QUESTIONS 

Compare the body of a protozoon with the body of a grasshopper. 
In what are they alike? In what different? 

How do the amoeba and paramecium compare? 

Explain how the Protozoa eat, digest food, produce more Protozoa, 
and protect themselves. 

How do these vital processes compare with the similar vital processes 
in the grasshopper? 

In what ways are Protozoa injurious to man? Are they parasitic? 
REFERENCES 

Galloway, First Course in Zoology, Chapter X. 

Hegner, Introduction to Zoology, Chapters IV, V, VI. 

Jordan and Kellogg, Animal Life, Chapters II, III. 

Kellogg, Animals and Man, Chapter V. 

Osborne, Economic Zoology, Chapter II. 


CHAPTER X 


THE SIMPLER METAZOA 

128. Metazoa. — The Protozoa just studied are single, 
free, living cells, while the grasshopper is made up of thou¬ 
sands of cells. The grasshopper is called a metazoon (met-a- 
zo'on: Greek, meta,. later; zoon, animal) because there are 

many cells in its body. 
The Protozoa and the Meta¬ 
zoa are alike in that both 
take in food, breathe, give 
off waste matter, and repro¬ 
duce their kind. 

There are a number of 
organisms concerning which 
scientists disagree as to 
whether they are plants or 
animals. In zoology, these 
forms are known as Colonial 
Protozoa or simple Metazoa. 
We shall study two of these 
(gonium and volvox) and then examine the sponges, which 
all scientists agree are Metazoa. 

129. Gonium. — Gonium is an animal made up of sixteen 
separate cells held together by a mucilage-like secretion of the 
cells. Each cell works independently in getting food, breath¬ 
ing, giving off waste, and in reproduction. The colony 
moves by lashing the water with long protoplasmic threads 
(flagella), two of which project from each cell. The advan¬ 
tage in rate of movement resulting from the union of cells is 

152 



Figure 142 . — Gonium. 






DIVISION OF LABOR 


153 


illustrated in rowing. Eight men in a large rowing shell 
can go faster than one man in a single, small shell. In repro¬ 
duction, the sixteen cells fall apart, and each one grows into 
a new colony. 

130. Volvox.— Volvox. is a colony of hundreds of tiny 
green cells embedded in a hollow gelatinous sphere. Each 
cell has two flagella. For a time all the cells are alike and 
share equally in the work of the colony. But in reproduction 
only a few cells take part. In the simplest method, a few 
cells grow large and escape into the hollow sphere. There, 
they divide and grow into new 
colonies. Finally, the mother 
colony breaks, and the daughter 
colonies escape. 

The more complex method is 
like the reproduction of higher 
animals. Certain cells in the 
colony grow large and escape 
into the hollow sphere. They 
are the egg cells. Other cells of 
the colony enlarge and divide 
into large numbers of slender, free-swimming cells called 
sperm cells. The sperm cells escape into the hollow sphere 
and swim about. One sperm enters an egg cell and unites 
with it, forming a single cell, the fertilized egg cell, which 
can develop a new colony. 

131. Division of Labor. — In gonium, the cells are alike in 
form and function, but in volvox, we find that a few cells 
have been changed in form in order to perform better the 
special work of reproduction. This is the first step in the 
division of labor. 

This is well shown in the higher animals, where certain 
cells are grouped together for a given work. The diges¬ 
tive system contains cells which work to make solutions of 
the food eaten. These solutions nourish the whole body, 




154 


THE SIMPLER METAZOA 


not the cells of the digestive tract alone. Certain other 
cells are modified in such a way for secreting and holding 
lime that they form bones by which the whole body is bene¬ 
fited. 

Some cells are grouped to form muscles to be used in 
securing food and in enabling animals to escape from their 
enemies. Other cells are for the purpose of conveying and 



Figure 144. — Bath Sponge. A Skeleton. 


interpreting impressions, so that the animal may hear the 
approach of an enemy, or detect the presence of food. It is 
largely the carrying out of this “ division of labor ” that tells 
us the rank of an animal or a plant in biological classification. 

In the business world we have a somewhat similar division 
of labor. Years ago the cobbler made all the parts of a shoe. 
In our large shoe factories to-day we find no one man making 
an entire shoe. One man runs the machine that cuts the 
leather and he does no other part of the work. He may have 
been a cutter twenty years, and he works rapidly and ac- 




STRUCTURE 


155 


curately. Another man runs the machine which sews 
uppers to the soles. He, too, is a rapid and skillful worker. 
Other men have their special lines of work to do. In the 
end they produce more shoes and better shoes than this 
same number of men could, if they were all cobblers and each 
finished his product. 

132. Sponges. — Sponges are simple Metazoa. In them 
we find division of labor carried out in a more complex way 



Figure 145. —The Sponge Known as Grantia with Part of the 
Wall Removed. 

Water enters through minute pores in the side of the sponge and escapes 
through the large opening at the top. 

than in gonium and volvox. Simple sponges have a body 
in the form of a hollow cylinder. Water enters through the 
sides of the body and passes out through a hole in the top. 
A simple sponge, called Grantia , grows in salt water attached 
to docks or other objects submerged along the seashore. 
On examination, it will be observed that grantia is less 
simple than volvox. 

133. Structure. — Grantia is composed of three layers of 
cells which show division of labor. The inner layer is called 
the endoderm (en'do-derm). It consists of cells provided 






156 


THE SIMPLER METAZOA 


with flagella which, by their movement, produce a current 
of water through the central cavity. The water enters 
through the holes in the sides (inhalent pores) and is forced 
out through the opening at the top pore (exhalent pores). 
The water contains food particles which the cells of the 
endoderm have the power to take in and digest. The food 
solution is passed to the other cells in the .sponge body by 
the process of osmosis. This is a process in which gases or 
liquids of unequal densities, separated by a plant .or animal 
membrane, tend to mix and become alike, the liquids or 
gases passing through the membrane. 

Thus the food digested is passed on and nourishes the cells 
of the middle and outer layers. The cells of the middle 
region form spicules (spic'uls) of lime (Figure 147) that pro¬ 
ject through the other layers and strengthen the whole body. 
The outer layer or ectoderm (ek'to-derm) serves as a protec¬ 
tive layer and with the help of the spicules gives definite 
shape to the body. 

LABORATORY STUDY 

The sponge which we ordinarily handle is simply the skeleton, and is 
easily kept from year to year. Examine several' kinds of sponge skele¬ 
tons and compare their shape, size, and the nature of the skeleton. How 
much water will the pores of the sponge hold ? Microscopic sections of 
Grantia are necessary if you are to make out the inhalent pores, the 
central cavity, and spicules. 

134. Reproduction. — At certain times of the year the 
sponge reproduces by means of two kinds of cells (eggs and 
sperms) developed in the middle layer. A sponge may 
develop both eggs and sperms, but usually develops 
only one kind at a time. Cells from the middle layer 
move in between cells of the endoderm and grow large and 
round. These are the eggs (female cells). Other cells move 
into the endoderm layer and divide into many small ciliated 
cells (the sperm or male cells). The sperms are set free and 
escape into the water of the central cavity and out from the 



ECONOMIC IMPORTANCE 


157 



body of the parent sponge. A sperm enters the body of 
another sponge and when it finds an egg, fuses with it, thus 

forming the fertilized egg. The fertilized _ 

egg then begins to grow, and after a defi¬ 
nite period breaks away from the parent, 
moves about for a time, and then settles 
down, attaches itself, and grows into a 
mature sponge. The immature sponge 
has the power of locomotion, but the 
mature form has lost this power. Never¬ 
theless the sponge is an animal. 

Reproduction that comes about through 
the fusion of an egg and a sperm is called 
sexual reproduction. The other method 
of reproduction, called asexual reproduc¬ 
tion, also occurs among sponges. By 
this method, sponges form little buds or 
branches which develop into new sponges. 

135. Spongilla. —Spongilla (spunj-il'la) 
is a fresh-water sponge. At the approach 
of cold weather, certain reproductive 
bodies are formed, known as winter-cells, 
and these escape from the sponge. They settle down to the 
bottom of the pond or stream and remain dormant until the 

approach of warm weather, when 
they grow into new sponges. 
They have a thick protecting 
coat which enables them to resist 
unfavorable conditions. 

136. Economic Importance. — 
The spicules of the different 
sponges form a large part of their 
so-called skeletons. These spic¬ 
ules are, in some cases, com¬ 
posed of lime and form the limy 


Figure 146. 

The sponge begins 
in a single cell that 
divides into two, then 
into four. After a 
while the cells be¬ 
come arranged as in 
A and the young 
sponge swims about; 
as it grows it be¬ 
comes attached and 
changes shape as in B. 



Figure 147.— Sponge Spicules. 
Not all these different kinds are 
found in each sponge. 










158 


THE SIMPLER METAZOA 


sponges. In others, they are of silica and form the glassy 
sponges. Sometimes fresh-water sponges grow in the water 
mains of cities and towns, causing the pipes to become 
clogged. 

The more important sponges have a skeleton made up of 
a hornlike substance which is flexible. This is the sponge 
of commerce, great quantities of which are gathered from the 
sea by divers and by dredges. The living tissues are allowed 
to decay, and the skeletons are then washed and dried. 
Some are bleached to form the white sponges. The sponges 
of best quality come from the Mediterranean Sea and the 
Red Sea. 

The value of the sponge fishery in the whole world annually 
amounts to about $3,500,000. 

137. Relation to Other Animals. — No animal is known to 
eat the sponge. Sponges themselves feed on minute particles 
of food, which are carried in by the currents of water pro¬ 
duced by the cilia of the endoderm. Some marine animals 
use the porous body of the sponge as a retreat. 

Certain sponges live in close relationship to higher forms 
of animals. One kind is always found growing on the legs 
of crabs. The movement of the crab carries the sponge to 
water richer in oxygen and food, and the crab is hidden from 
its enemies by its sponge covering. Each animal gains by 
this inter-relationship. Where two such animals as the crab 
and sponge live in this way the relationship is known as 
symbiosis (sym-bl-o'sis: Greek, syn, with; bios, life). 

SUMMARY 

The transition from simple Protozoa, through the Colo¬ 
nial Protozoa, to the Metazoa is simple and direct. In 
gonium and volvox, the beginning of division of labor is 
noticed; that is, one part of the body becomes dependent 
on another part for certain definite things. For example, 
one cell is devoted to securing food, while another produces 


REFERENCES 


159 


eggs or sperms. The sponges are simple Metazoa in which 
the division of labor has taken the form of producing three 
layers, — the ectoderm, or outer layer; the endoderm, or 
inner layer; and a loosely formed middle layer. Grantia 
is a simple sac-shaped sponge which reproduces both sexually 
and asexually. The general manner of development by the 
sexual process is essentially the same in all the higher animals, 
including man. The bath sponges are the only ones of 
economic importance. 

QUESTIONS 

What can the single-celled protozoon do? Compare with the Colo¬ 
nial Protozoa, gonium and volvox. Explain the meaning of division 
of labor in an animal. In what respects do sponges differ? Of what 
use are they? Why are not all sponges useful? 

REFERENCES 

Hegner, Introduction to Zoology, Chapter VI. 

Jordan and Kellogg, Animal Life, Chapter II. 

Osborne, Economic Zoology, Chapter III. 


CHAPTER XI 


CCELENTERATES. HYDRA-LIKE ANIMALS 

138. Ccelenterates. — The Coelenterates (se-len'te-rats : 
Greek, koilos, hollow; enteron, intestine) are simple Metazoa, 
a little higher in development than the sponges. In this 
group are hydras (hi'dras), hydroids (hl'droids), jelly-fishes, 
sea-anemones (a-nem'o-nez), sea-fans, and corals. 

139. Structure of Hydra. — The hydra is an interesting 
fresh-water animal about a quarter of an inch in length. Its 
body is shaped like a little cylindrical bag with only one open¬ 
ing, the mouth, which is surrounded by a few, usually six, 
delicate, thread-like arms called tentacles (ten'ta-kls). The 
body is composed of three layers, the outer layer, ectoderm; 
the middle layer, the mesoglea (mes-o-gle'a: Greek, mesos , 
middle; gloios, glutinous substance); and the inner layer, 
endoderm. 

Each layer does some particular work for which the others 
are not fitted. For example, the outer layer contains cells 
which are especially sensitive to stimuli and many modified 
muscle cells that enable the animal to move about. The 
inner layer contains cells provided with flagella which catch 
the food particles for the inner cells to digest. The muscular 
action of the outer layer moves the entire animal. The sensi¬ 
tive cells enable the animal to recognize its prey. The food 
digested by the inner layer is used by all the cells of the body. 
Thus we see an advance in the division of labor over that 
shown in the sponge. We shall observe a still greater in¬ 
crease in division of labor as we study higher animals. 

Tentacles are hollow, finger-like branches connected with 
the body cavity. They are provided with stinging cells 

160 



LOCOMOTION 


161 


which help the hydra to capture living water fleas, and the 
like. These stinging cells have darts which are automatically 
discharged when the ten¬ 


tacles come in contact 
with little animals. The 
darts stun the prey and 
render escape impossible. 
The tentacles surround 
the food and carry it to 
the mouth, which opens 
directly into the food 
cavity. The action of the 
tentacles in doing this 
work suggests the idea 
that each tentacle has 
some way of realizing the 
efforts of the others. 

We should keep in 
mind that in the Metazoa 
the united cells are in 
connection with one an¬ 
other through the cell 
walls. This is true even 
if we are not able to trace 
the connections with the 
microscope. In the higher 
animals we shall find that 
connections between cells 
are made by means of 
nerve cells. The develop¬ 
ment of a nervous system 
only carries out division of 
labor to a greater degree. 

140. Locomotion. — The 



Figure 148. — Fresh-Water Hydras. 


They are usually found attached to a 
water plant as in this drawing. The ex¬ 
panded hydra has a nearly full-grown 
hydra attached to one side and a small 
bud near the base. Both these young 
hydras were produced by the method of 
reproduction known as budding. The 
larger but very short hydra near the sur¬ 
face of the water is in a contracted con¬ 
dition and would be as long as the larger 
of the two expanded ones, if it were feed¬ 
ing. The small crustaceans shown in 
this drawing constitute the main food of 
hydra. How do they capture them? 


adult hydra is usually found 


attached as in Figure 148. In this condition the only move- 








162 CCELEN TER A TES. HYDRA-LIKE ANIMALS 


merits possible are such as take place in the expansion and 
contraction of the whole body. The tentacles wave about 

in the water and as the hydra 
expands, the body may move 
first in one direction, then in 
another. In this sense the 
hydra does not move about 
as does a grasshopper or a 
paramecium. At infrequent 
intervals, however, the hydra 
detaches itself and moves 
from place to place by at¬ 
taching the tentacles, then 
the base, then the tentacles 
much like a boy turning 
handsprings. 

141. Nutrition. — The hy¬ 
dra feeds almost entirely 
upon minute animals. The 
forms that furnish the greater 
amount of their food are shown in Figure 54. These 
animals belong to a much higher group of animals than the 
hydra; namely, the Crustacea, the group to which the cray¬ 
fish and crabs belong. 

These animals which have 
an exoskeleton like in¬ 
sects are rendered inac¬ 
tive by the stinging cells 
on the tentacles. The 
paralyzed animal is then 
brought to the mouth 
by the tentacles, Figure 
148, and swallowed. Within the body, the nutritive parts 
are digested by enzymes as in other animals and ab¬ 
sorbed, passing by osmosis to all the cells. The undigesti- 




of Hydra. 



















REPRODUCTION 


163 


ble skeleton of the animals eaten is cast out through the 
mouth. 

142. Respiration and Excretion. — By osmosis, oxygen is 
absorbed from the water by the cells of the ectoderm. The 
water that enters the mouth carries 
oxygen, and by osmosis it is absorbed 
by the cells of the endoderm. At the 
same time the carbon dioxide from the 
cells is thrown off into the water. 

143. Irritability. — The hydra is able 
to appreciate a variety of different 
kinds of stimuli such as jars, a moving 
animal or an enemy. It is able to con¬ 
tract, expand, and move the tentacles 
in such a way as to bring food to the 
mouth although it does not possess 
nerves or a brain. When a special 
study of the structure of the hydra is 
made, nerve cells are found which 
assist it in responding to stimuli. In 
the Protozoa there are no special nerve 
cells but the hydra shows the beginning 
of the formation of a nervous system. 

144. Reproduction. — The hydra re¬ 
produces both sexually and asexually. 

In sexual reproduction eggs and sperms 
are produced by the ectoderm cells. 

The sperm cells escape into the water 
and, like sperm cells of all other animals, have the power of 
locomotion. The fusion of the egg cell and a sperm cell 
starts growth which results in the division of the egg cell into 
many other cells. Hydras also reproduce asexually by bud¬ 
ding. The buds soon separate from the parent and begin 
an independent life. Like the developing sponge, the develop¬ 
ing hydra grows until it finally becomes a fully formed hydra. 



Figure 151. — Photomi¬ 
crograph of Hydra 
Bearing Eggs Illus¬ 
trating One Form of 
Reproduction. 

Reproduction by budding 
is shown in Figure 148. 




164 CCELEN TER A TES. HYDRA-LIKE ANIMALS 


LABORATORY STUDY 

The living brown or green hydras can usually be found in the spring or 
fall in most fresh-water ponds. They are easily collected by gathering 
the floating leaves and overhanging grass that is immersed in the water. 
Place this collection in a glass jar in the laboratory. In a couple of days 
the hydras will have moved from the grass to the sides of the jar. They 
can be examined by a small magnifying glass in the jar or be transferred 

to a watch glass and observed under 
the low power of the microscope. 
Watch the hydra contract, when jarred 
or touched. Note that the tentacles 
become very short. Try feeding with 
a small bit of raw meat. Make out the 
transparent ectoderm and the darker 
endoderm. Are there any buds ? What 
happens to the buds when the parents 
contract ? 

145. Hydroids. — Hydroidsare 
marine, hydra-like animals which 
are united in groups forming a 
tree-like colony (Figures 153, 
156, a ). They are often mistaken 
for plants. When the young 
hydroid first begins to grow, it 
looks like the fresh-water hydra 
(Figure 156, k). 

As the hydroid grows, branches 
form and on the end of each 
branch, tentacles and a mouth 
appear. Each branch is able to capture food and, after it 
takes what it needs, the surplus is distributed to other parts. 
This is easily brought about, as a common digestive cavity 
connects all the branches. The hydroid is termed a colony 
because all the branches are united and help one another 
in getting enough food for the colony. 

Some of the hydroids form curious buds which develop 
into medusce (me-du'se). (See Figure 152, A .) As soon as the 



Figure 152. — Photomicro¬ 
graph of the Colonial Hy¬ 
droid Obelia with Medusae 
Forming at A. 




HYDRO IDS 


165 



Figure 153. — A 
Hydroid Colony. 

It resembles a 
plant and is often 
mistaken for one. 



Figure 154.— The Medusa Known as 
Pelagia. 

It is found swimming on the surface of 
the water far from land. 


medusae are set free from the hydroids, they swim about and 
capture their own food. Each medusa is provided with either 


ovaries (o'va-riz), organs which 
produce egg cells, or sperma- 
ries (sper'ma-riz), organs which 
produce sperm cells. When the 
eggs and sperms mature, they 
are discharged into the water. 
A single sperm cell must fuse 
with an egg cell before the egg 
can begin to grow. The union 
of these two cells is called 
fertilization. The egg grows 
into an embryo (em'bn-o), an 
immature stage varying with 
different animals, and this 
gradually changes into a small 
hydroid. The several steps 



When the medusa buds shown 
forming at A in Figure 152 mature, 
they are set free in the water and 
look like this photomicrograph of a 
free swimming medusa (greatly 
enlarged). 













166 C (ELEN TER AT ES. HYDRA-LIKE ANIMALS 



Figure 156. — Pennaria 
Tiarella. 


in this complicated series of 
changes are illustrated in Figure 
156. The hydroids and medusae 
show a form of reproduction 
called alternation of generations, 
that is, they reproduce alternately 
sexually and then asexually. 

146. Sea-anemone. — Sea- 
anemones are animals allied to 
the hydra. The interior of the 
body cavity is subdivided by 
many partitions which increase 
the digesting and absorbing sur¬ 
face. The sea-anemone repro¬ 
duces by eggs and sperms. 

The resulting embryo is free at 
first, but later becomes fixed to 
some object and develops into 
the sea-anemone. There is no 
medusa stage. 

147. Coral. — Geographies tell 
us of the many coral islands and 
reefs built up by the coral ani¬ 
mals. These animals are coelente- 


a, The hydroid colony; b, one 
of the female medusae, much 
enlarged; c, the egg of the 
medusa beginning to segment 
after it has been fertilized; 
d, e, f, further segmentation 
stages; g, the blastula stage; 
h, the free swimming larva 
(planula) ; i, /, and k show the 
gradual transformation of the 


rates, most of them closely allied 
to the sea-anemone, but the coral 
animal secretes about the body 
and along the partitions calcareous 
(kal-ka're-us, limy) skeletons 
which form the stone-like masses 
of the coral rock. The upper 
portion of the coral rocks is alive 


larva into a hydra-like colony. 

Branches grow on the stage shown in k until a colony like a results. This 
is the form that alternation of generations takes in this hydroid. (Arranged 
from a monograph on Pennaria by C. W. Hargitt.) 





ECONOMIC IMPORTANCE 


167 


with these coral animals. The lower portion is made up of 
skeletons only. Succeeding generations build upon the work 
of their ancestors. 

Corals reproduce much as trees produce branches, but at 
certain periods eggs and sperms are produced as in the sea- 
anemone. Then the embryo settles down, secretes its own 
skeleton, and this is added to the work of other corals. 

Sea-fans and sea-plumes are coelenterates which have the 
forms suggested by their 
names. A dried speci¬ 
men of either looks as 
. if a branch had been 
dipped in a solution and 
coated. The interior is 
of a horny substance. 

The exterior is covered 
with a limy secretion. 

148. Economic Im¬ 
portance. — The corals 
alone of the coelente¬ 
rates are of economic 
importance; they add 
to many islands, protect others from being washed away, 
and in some cases form entirely new islands. 

SUMMARY 

The hydra-like animals represent an advance in the divi¬ 
sion of labor. The layers of their bodies are more definite 
and do their work better than in the sponges. Hydroids 
and the corals illustrate the formation of a colony. In some 
of the colonies the division of labor is more extensive than in 
others. The economic importance of some corals has been, 
and continues to be, very great, as they contribute to the 
formation of land in the ocean ; on the other hand, such corals 
as sea-fans serve merely as odd ornaments. 




168 CCELENTERATES. HYDRA-LIKE ANIMALS 


QUESTIONS 

Explain fully how the hydra gets its food and how some of this food 
finally nourishes the ectoderm cells. Compare the hydra and the 
hydroid. In what are they alike? In what are they different? How 
does the hydra reproduce? How does the hydra get its oxygen? Ex¬ 
plain how the coral animal has been able to form islands. 

REFERENCES 

Darwin, Structure and Distribution of Coral Reefs. 

Hegner, Introduction to Zoology, Chapter VIII. 


CHAPTER XII 


THE STARFISH FAMILY 
Optional 

149. The Starfish Group. — This group of animals in¬ 
cludes the well-known starfish, the sea-urchins, sea-lilies, and 
several soft-bodied forms such as the sea-cucumber. The 
technical name for these different animals is echinoderm 
(e-km'6-derm : Greek, echinos , spine ; derm, skin), mean¬ 
ing spiny-skinned animals. Most of these animals have a 
skeleton. Unlike that of 
man it is on the outside 
and is composed of calcare¬ 
ous plates. In some forms, 
like the starfish, the plants 
are embedded in the skin, 
while in the sea-urchin the 
plates fit edge to edge, 
forming a shell. The plates 
support many spines which 
project out from the body 
giving the spiny appearance 
characteristic of the group. 

Both the skeleton and soft 
parts are arranged in a radial manner. The presence of 
spines and the radial arrangement are two characters by 
means of which one can recognize most of the echinoderms. 

150. The Starfish. — Starfishes are found in salt water. 
They are composed of a central region, called a disk, from 
which extend five arms or rays. On the disk is a porous 

169 





170 


THE STARFISH FAMILY 


circular plate. It is known as the madreporic plate (mad-re- 
phr'ik: Greek, mater , mother; poros, soft). It serves to 
take water into a series of vessels by means of which the 
animal moves and holds on to rocks and shells at the sea 
bottom. 

Internal Structure. — If the upper portion of the animal 
is removed carefully, the internal structure can be examined. 
Each ray is nearly filled with masses of yellowish green 
substance. This is a gland which forms the digestive fluids 
used in the stomach. The wrinkled mass in the region 



A, liver; B, stomach; C, mouth; D, stone canal through which the 
water enters that is used in the organs of locomotion; E, tube feet; F, re¬ 
productive glands. 


beneath the disk is the stomach. The mouth is just below 
the stomach on the lower or oral side of the body. At the 
angles of the arms and extending into each ray are the 
reproductive glands, which vary in size at different ages and 
seasons. According to the sex of the individual these glands 
produce either eggs or sperms, which are discharged into the 
water. 

LABORATORY STUDY 

Dried specimens of starfish serve well for general study. These may 
be compared with specimens which have been preserved in alcohol or 
formalin. Work out the several parts such as disk, arms, madreporic 
plate, spines, groove of the feet, and position and form of the mouth. If 
skeletons of sea-urchins are available, they are interesting for comparison. 








FOOD TAKING AND NUTRITION 


171 


151. Locomotion. — Locomotion in the starfish is ac¬ 
complished by means of the four rows of tube feet which 
extend from the rays on the oral surface. The tube feet of 
the arms in front are attached to the surface over which the 
starfish wishes to move. Then the tube feet of the arms to 
the rear are released and the starfish draws up these arms, 
raising the disk region 
up. The tube feet in the 
arms to the rear are at¬ 
tached to the surface 
while the arms to the 
front are released and 
pushed ahead as the disk 
is lowered to the surface. 

This motion is carried on 
slowly until the starfish 
has reached its destina¬ 
tion. Each tube foot has 
an adhesive disk and is 
connected with a small 
reservoir inside of the 
arm. 

152. Food Taking and 
Nutrition. — The starfish 
takes its food in an un¬ 
usual manner. Most ani¬ 
mals move the food to 



Figure 160. — The Embryo of the 
Starfish. 

It develops into a free swimming larva 
that does not look at all like the parent. 
After a time the young starfish is formed. 


move 

the mouth, swallow it or engulf it, and digest it within the 
body cavity. In the case of the starfish we find that the 
stomach is projected through the mouth and made to sur¬ 
round its food. In this position it digests and assimilates 
the food and then withdraws its stomach through the mouth 
and moves on slowly to some other place. A common food 
of the starfish is the clam. Various explanations have been 
offered as to how the starfish is able to secure the soft flesh 







172 


THE STARFISH FAMILY 


of a clam or oyster which is protected by hard shells. It 
is now known that the starfish attaches its tube feet to each 
side of the clam and by constantly pulling tires out the 
strong muscles that hold the shell together. As soon as 

these muscles relax, the 
shell opens. The stomach 
is then pushed out, en¬ 
veloping the clam. The 
digestive fluid contain¬ 
ing enzymes is secreted 
and the dissolved clam is 
absorbed as food. 

153. Respiration.— 
Oxygen is taken from the 
water and carbon dioxide 
given off through little 
thin-walled, gill-like pro¬ 
cesses which cover the 
upper surface of the disk 
and arms. These gill-like processes project through holes 
in the exoskeleton. 

154. Excretion. — There are no special organs in the star¬ 
fish for the removal of wastes. 

155. Nervous System. — The starfish possesses a definite 
arrangement of nerves. In this respect, it shows a marked 
advance over the hydra. There are five nerves, one in each 
arm, all of which join a nerve collar that surrounds the mouth. 
There is no brain. This nervous system of five nerves and 
a nerve ring receives stimuli and controls the slowly contract¬ 
ing muscles. 

156. Life History of the Starfish. — In the starfish the 
sexes are distinct. The female discharges eggs into the 
water and the male discharges sperm cells into the water. 
The sperms being constantly in motion, are likely to meet 
the eggs. When this occurs, a sperm cell enters an egg, 





ECONOMIC IMPORTANCE OF THE GROUP 173 



starting the growth and development of the starfish larva. 
The larva is at first wholly unlike the starfish in form; there 
is not even a suggestion of the starfish outline. After the 
larva has attained a certain size a tiny bud appears which 
develops into the little 
starfish. The bud de¬ 
velops on the larva and 
feeds on it. From this 
bud the adult starfish de¬ 
velops. This is another 
example of metamorpho¬ 
sis (Figure 160). 

157. Other Echino- 
derms. — The sea-urchins 
are thickly covered with 
spines and have tube feet 
which, in many cases, 
may be greatly extended. 

When the spines are re¬ 
moved, an exoskeleton is 
revealed, which plainly 
shows the radial arrange¬ 
ment characteristic of the 
echinoderm group. 

158. Economic Impor¬ 
tance of the Group. — 

Of echinoderms the star¬ 
fish alone has an economic 
bearing. It is harmful. 

Living as it does in the 

region of the oyster and clam beds and feeding almost ex¬ 
clusively on them, the starfish annually destroys thousands 
of dollar worth of clams and oysters. By removing the sea¬ 
weed where the immature starfish gather and by dragging the 
oyster and clam beds great numbers of starfish are destroyed. 


Figure 162. — The Common Sea- 
cucumber. 

An Echinoderm without any skeleton 
for protection. It has become adapted to 
living in the sand much like the worms. 



174 


THE STARFISH FAMILY 


In former times the fishermen used to break starfish to 
pieces on the side of the boat and throw them back into the 
water. It is now known that by so doing they were but 
increasing the number of starfish, for starfish have the 
power to re-grow the parts broken off. Each complete arm 
could reproduce an entire starfish. This power to restore 
lost parts is known as regeneration (re-jen-er-a/shun). Many 
of the lower animals have this power to a marked degree, 
and all animals have it to some degree. 

SUMMARY 

The starfish group of animals is known by the presence 
of spines in the skin and a radial arrangement of the organs. 
Their chief economic relation to man consists in their great 
destructiveness to oyster and clam beds. 

QUESTIONS 

Why are starfish so called? How can they be distinguished from 
other animals ? How do they move ? Where do they live ? On what 
do they feed? How do they secure oxygen? 

REFERENCES 

Brooks, The Oyster. 

Osborne, Economic Zoology, Chapter VIII. 

Poulton, All About the Oyster. 


CHAPTER XIII 


THE WORM GROUP 

159. The Worm Group. — Here are found several distinct 
groups of animals that in advanced text-books of zoology 
are treated separately. The word “ worm ” is an old term 
which properly describes such animals as the earthworm, 
sea-worm, leech, tapeworm, flatworm, and a few others. 
The word “ worm ” cannot be correctly used for such larvae 
of insects as the “ apple tree worm ” or “ currant worm.” 

The worm group is divided into two classes: those 
whose body is composed of numerous segments (seg'ments) or 
rings, such as the earth¬ 
worm, the sea-worm, and 
the leech; and those 
whose body is not seg¬ 
mented, such as the tape¬ 
worm and flatworm. The 
first class comprises the 
true worms, which are 
known as Annelida 
(a-nel'i-da). The second class, the unsegmented worms, have 
no single technical name, and are not believed by scientists 
to be true worms. They comprise a number of worm-like 
animals which have hardly any features in common. Here 
are found the fresh-water planarians, the parasitic tape¬ 
worms, liver flukes, and numerous round worms, of which 
the hair worm is an example. 

The planarian worm is one of the simplest of these un¬ 
segmented worms. It is found under stones submerged 

175 



Figure 163. — A Planarian Worm. 


These fresh-water worms are abundant 
during the summer and are easily col¬ 
lected for class study. 



176 


THE WORM GROUP 


in stagnant water and in streams. It is frequently brought 
into the laboratory and can easily be kept alive in aquaria. 

The liver fluke is a parasitic flatworm which each year 
causes the death of many sheep by injuring their livers. 1 
Like some other parasitic animals the liver fluke requires 
two hosts to complete its development. The hosts of the 
fluke are the sheep and certain snails. The adult liver 
flukes form eggs and sperms in the liver of the sheep. The 
fertilized eggs partially develop in the sheep; then as 
embryos they pass down the bile duct 
into the intestine and then out of the 
body. 

The ciliated (sil'i-a-ted) larva then 
makes its way into water or along dew- 
covered grass. If it comes in contact 
with a water snail in the water or a land 
snail on the grass, it enters the body of 
its second host, otherwise it dies. Once 
inside the body of the snail it completes 
a complicated development. By a 
bud-like process many young flukes are 
formed which finally emerge from the 
snail and make their way to the grass 
stems on which they encyst themselves. 
If this grass is eaten by a sheep, the diges¬ 
tive fluids set free the young fluke, which 
goes up the bile ducts to the liver, where it grows to maturity. 

160. Trichina. — Another unsegmented worm that is of 
economic importance is the Trichina (tri-ki'na), now gen¬ 
erally called Trichinella (tri'kl-nel'la). This worm lives 
in the intestine of mammals and from the intestine mi¬ 
grates into the muscles of its host. In the muscle it becomes 
encysted and remains until the flesh is eaten by some other 

1 The Animal Parasites of Sheep. Dr. Cooper Curtice. Bureau Animal 
Industry, United States Department of Agriculture, 1890. 



Figure 164.— Trichi¬ 
nella. 

A picture of this para¬ 
sitic worm in the mus¬ 
cles of man. Note the 
membranous sac which 
encloses it. This is the 
form of the sac after the 
worm comes to rest in 
the muscles. The worm 
is then said to be en¬ 
cysted. 





TRICHINA 


177 


mammal. When pork, infected with this parasite and 
insufficiently cooked, is eaten by man the cysts are dissolved 
by the digestive fluids and the worms are freed. 

These worms then develop eggs and sperms which after 
uniting mature into young worms and migrate through the 
intestine into the muscles. The activity of the worms at 
this stage causes a serious inflammation of the tissues and a 
disease known as trichinosis (trik-m-o'sis), which is often 
fatal. Hogs contract trichino¬ 
sis by eating refuse that con¬ 
tains the encysted worms. 

Government inspectors ex¬ 
amine pork which is to be 
exported or sold in large 
quantities to see that it is free 
from these parasites. The 
smaller sales of pork by local 
dealers are not inspected and 
the only way to be sure of the 
harmlessness of the meat is to 
cook it thoroughly. 

Hair Worm. — The only im¬ 
portance that can be attached 
to these worms is the myth 
about their origin. In almost 
every school will be found students who believe that horse 
hairs placed in water will develop into “ hair snakes.” It 
would be a pity if a student still believed this after a course 
in biology. 

Let us see how such a belief can originate and often be 
thought to be proved. The hair snakes live for a time in 
water and often in the watering troughs where horse hairs are 
also found. Boys, and men too, sometimes put horse hairs 
in water and then after a few weeks examine the water and 
find these hair snakes. They conclude, since they put in the 







178 


THE WORM GROUP 


hairs and later found the “ hair snakes/’ that the hairs grew 
to form the snakes or small round worms. If they had 
been as careful to look before any hairs were put in, they 
would have seen these “ hair snakes ” swimming about. 
A better test is to take a bottle of distilled water, put in 
the hairs, and watch for developments. Such a test would 
show that no hairs turn into hair snakes. 

Hair snakes have a complete life history as clearly defined 
as other worms. They lay eggs which fuse with sperms 
and form larvae. These larvae live as parasites in the bodies 
of insects and fishes and when mature make their way out 



Figure 166. — Hair Worm Living as a Parasite in the Body of the 
Grasshopper. 


of the bodies of their hosts. It would be natural, then, to 
find them in pools where horses drink and these parasitized 
fishes live, or in watering troughs into which grasshoppers 
may have jumped, as they so often do. 

We know at present no way in which lifeless matter can 
be made to live. A hair cannot become a worm and a 
crooked stick cannot grow into a snake. New life comes 
from the old. We sometimes read in the papers that some 
one has produced life from chemicals, but it is not believed 
at the present time to be possible. 

161. The Earthworm is the simplest and best animal to 
illustrate the annelid group of true worms. 

When one examines a living earthworm, the head end 





LOCOMOTION 


179 


can be determined as the one which first moves forward. 
Actually there is no head ; nor are there special sense organs. 
The muscles in the front end are stronger and the body 
rounder than in the back end. The back, or dorsal (dor's’l) 
part, of the worm which is exposed to the light is darker in 
color than the rest. This surface is rounder than the opposite 
(under) one which is in constant touch with the dirt when 
the worm is crawling. The flat surface upon which the 
worm crawls is the ventral (ven'tral) surface. 

The body of the earthworm is made up of a number of 
segments (rings) which are marked off by shallow grooves. 
Some of the segments in the front end are larger than those 
that make up the back end, but all are similar in shape. 
The number of segments depends mostly upon the age of the 
earthworm. It is from 60 to 150 in full-grown worms. 

162. Locomotion. — The earthworm crawls by means of 
short, stiff bristles used as legs, the setce (se'te: Latin, seta , 
bristle), which are found in all the segments except the 
first two or three. These setae are arranged in four rows, 
two in each row. To understand how the setae are used in 
the locomotion of the earthworm it is necessary to know 
that the body wall contains two muscular layers. In the 
outer layer the muscles running around the body are called 
circular muscles. The inner layer, consisting of a number 
of bands running in the direction of the length of the body, 
are called longitudinal muscles. The contraction of the 
circular muscles lengthens the body and the contraction of 
the longitudinal muscles shortens it. The setae are con¬ 
nected with the longitudinal muscles. By pointing the 
setae backward and bracing them against the ground, the 
worm can push itself forward. By pointing the setae forward 
the worm can instantly change the direction of its movement. 
This is the reason why it is so difficult for a robin to pull 
an earthworm from its burrow. Often the robin will tear 
the worm apart, so firmly do these setae hold. 


180 


THE WORM GROUP 


LABORATORY STUDY 

One of the annelids should be studied with some care, as an illustra¬ 
tion of an invertebrate animal. How do you determine the anterior and 
posterior ends? Dorsal and ventral surfaces? The number of seg¬ 
ments? Compare several worms. The back region of the worm shows 
the most variation because new segments are being added. Where are 
the setae ? How does the earthworm move ? Place it on a glass. The 
front region of the body is most sensitive to touch. Test it. 

163. Food-taking. •— The food of the earthworm is chiefly 
the soil in which it burrows. By means of an upper lip, 
which is a specialized anterior segment, and the muscular 
walls of the pharynx it takes the earth into its body, and 
the muscles of the digestive tube advance the food along 
its course. The soluble and therefore digestible parts 
are absorbed, and the remainder (the greater portion) 
is passed along to the outside. Earthworms are not critical 
in the selection of their food, although they are not entirely 
without a sense of taste. 

164. Respiration. — Oxygen passes through the skin 
directly into the blood vessels. The blood carries the oxygen 
to all parts of the body. Carbon dioxide passes from the 
blood through the skin to the outside. This interchange of 
oxygen and carbon dioxide is brought about by osmosis. 

165. Excretion. — In each segment is found a pair of 
organs known as nephridia which look like little threads. 
These organs remove the liquid waste and carry it to the 
outside of the body. 

166. Internal Structure of Earthworms. — This is shown 
diagrammatically in Figure 167. The internal structure 
consists of an outer tube, the body-wall, and an inner tube, 
the digestive tube. The space between the body-wall and 
digestive tube is known as the body cavity or ccelome (se'lum : 
Greek, koilos, hollow). Thin sheets of membrane pass from 
each furrow between the segments to the digestive tube. 

Beginning at the front end the digestive tube is given 



INTERNAL STRUCTURE OF EARTHWORMS 181 


certain names for each distinct region, as follows: the 
mouth cavity; the pharynx (far'inks), with its thick muscular 
walls; the esophagus (e-sof'a-gus), thin-walled and small; 
the crop , a wide pouch ; the gizzard, where food is ground ; 
and the stomach-intestine, a large, thin-walled tract extending 
through the last two thirds of the length of the worm. 

The earthworm has an easily recognized nervous system 
which is found beneath the digestive tube. It consists of a 
continuous, minute, white thread with slight swellings in 
each segment. From these swellings, which are called 



Drawn from the side. (Esophagus also spelled oesophagus.) 

ganglia (gan'gli-a: Greek, ganglion, swelling or tumor), 
short branches extend to the digestive tube and other organs. 
These branches are known as nerves. Toward the front end 
the nerve-thread parts and becomes double. Each part 
passes around the front end of the pharynx and enlarges to 
form two ganglia, the largest found in the earthworm. More 
nerves grow from these two large ganglia than from any 
of the others and so the term “ brain ” is given to these two 
ganglia found in the dorsal surface of the pharynx (Figure 
167). 

The nervous system of the earthworm is clearly defined and 
occupies a central position, being found in the middle of 
the body. Although they have no eyes or ears, earthworms 











182 


THE WORM GROUP 


are able to tell the difference between night and day and to 
withdraw into their burrows if one steps heavily on the 
ground near them or takes a small stick and strikes the 
ground within a few feet of them. 

The organs of the earthworm are supplied with blood 
which is carried in a large dorsal blood vessel, a ventral 
blood vessel, and numerous branches. The blood is pumped 
by the contracting of the dorsal vessel 
and by the five pairs of tubes which pass 
from the dorsal to the ventral vessel 
around the esophagus. These five tubes 
are named aortic (a-or'tik) arches. 

LABORATORY STUDY OF INTERNAL 
STRUCTURE 

Work out the internal structure of the earth¬ 
worm. In dissecting, cut the skin along the 
dorsal surface, being careful to cut the many 
membranes that hold the digestive tube in place. 
Work out the size and position of the mouth 
cavity, pharynx, esophagus, crop, gizzard, and 
stomach-intestine. The white reproductive or¬ 
gans are located beside the esophagus. Locate 
the “brain,” the ventral chain of ganglia. The dorsal blood vessels and 
aortic arches should be located. Make a sketch locating the organs in 
their respective segments. 

167. Life History. — In the starfish group the sexes are 
distinct. The sexes in the annelids are distinct in some forms 
and in others the same individuals have both ovaries and 
spermaries. The sperms, however, that unite with eggs 
always come from another worm. During the season when 
the ovaries and spermaries are forming eggs and sperms, 
certain segments, usually six in number, beginning with the 
twenty-eighth segment, and known as the clitellum (kli- 
tel'lum), pour out a gelatinous secretion which hardens into 
a collar-like sac around the worm. 



Figure 168. —Front 


End of the Nerv¬ 
ous System of the 
Earthworm. 

The large mass is 
termed the “brain” 
because of its size 
and position. 




ECONOMIC IMPORTANCE 


183 


This sac is worked forward and as it passes the openings 
of the reproductive organs, eggs and the sperms from another 
worm are pushed into it. The sac continues to move forward 
and finally leaves the worm as a closed capsule. This 
capsule contains eggs, sperms, and fluid food. After the 
fusion of the eggs and sperms, the resulting embryonic 
worms begin to feed upon the fluid food in the capsule ; later 
they feed upon one another until but one may remain eventu¬ 
ally to bore or eat its way to the earth outside. From now 
on the food of the young worm is the 
soil. 

The earthworm is an example of an ani¬ 
mal which has both ovaries and spermaries. 

168. Self-protection. — The habit earth¬ 
worms have of remaining in their burrows 
during the daytime is their chief means 
of protection. During the daytime birds 
and other animals seek them out as food. 

They are perfectly helpless when captured. 

When a robin tries to pull an earthworm 
from its burrow, the projecting setae pre¬ 
vent the worm from being pulled out. 

Sometimes the body breaks under the 
strain but this does not kill the worm as 
the portion remaining in the burrow soon regrows the 
lost parts. During the winter or a dry season earthworms 
burrow deep into the ground and collect in groups for 
protection. 

169. Economic Importance. — The value of earthworms 
to agriculture is too great to be overestimated. In burrow¬ 
ing their way through the soil they leave passageways for 
water and air to enter, thus assisting plants to grow. They 
bring the fertile, swallowed soil to the surface. When the 
total number of earthworms is considered, it is obvious that 
they are the great natural cultivators of the soil. 



Figure 169. — Dero, 
a Common Fresh¬ 
water Annelid. 




184 


THE WORM GROUP 


170. Other Annelids. — The sand worm or Nereis (ne'- 
re-is), a marine or salt-water form, is another segmented 
annelid. It is more highly specialized than the earthworm, 
for it has biting mouth parts, tentacles, and eyes. It is an 
active swimmer at times. The development of the sand 
worm exhibits metamorphosis, while the earthworm hatches 
directly into a worm without metamorphosis. 

SUMMARY 

In the worm group are included the unsegmented worms, 
such as tapeworms, liver flukes, and hair worms; and the 
segmented or true worms such as the earthworms, sea-worms, 
and leeches. All these worms have more perfectly or¬ 
ganized parts than the sponges and hydroids. The body of 
the earthworm shows the first steps in the formation of 
definite front, back, and ventral regions. The digestive 
tube is also specialized into pharynx, esophagus, crop, 
gizzard, and stomach-intestine; and the name brain may 
be given to a slightly enlarged portion of the anterior end 
of the nerve cord. Small worms of various kinds are numer¬ 
ous in stagnant water. Some live as parasites in man and 
other animals, causing much suffering and loss of life. The 
earthworm as a cultivator of the soil has been of inestimable 
value to man. 

QUESTIONS 

What kinds of animals are called worms? Is it proper to call “ cur¬ 
rant worms” worms? Why not? What are they? How do you 
recognize the anterior, posterior, dorsal, and ventral regions? Compare 
the grasshopper or some other insect with the worm. Explain how the 
earthworm moves; makes its burrow. Compare the digestive tube 
with the digestive sac of the hydra. 

REFERENCES 

Darwin, Earthworms and Vegetable Mould. 

Jordan, Kellogg, and Heath, Animal Studies, Chapter VI. 

Sedgwick and Wilson, General Biology. 


CHAPTER XIV 


THE MOLLUSKS 

171. The Mollusks. — This group includes such animals as 
clams, oysters, snails, slugs, squids (skwids), and octopi 
(ok'to-pi). These forms differ from the crustaceans in 
having a soft, unsegmented body and, in most cases, a 
shell as their exoskeleton. The squids have a shell that 
is internal, and in some 
of the snails the shell is 
absent. 

172. Clams.— The fresh¬ 
water clam is a convenient 
type of mollusk to study. 

It is found in canals and 
in many streams and lakes. 

This clam has two shells Water enters throu £ h ls -> inhaIent 

. . . siphon, and leaves the body of the clam 

or valves and, when mov- through e ^ exhaIent siphon . 
ing naturally, the hinge is 

uppermost, while the opened valves allow the foot to be 
extended into the mud. The foot is a thick, muscular mass, 
not at all foot-like in appearance, but it enables the clam to 
move, although slowly and at an uneven rate. 

Structure. — The structure of the fresh-water clam shows 
how it has adapted itself to its peculiar method of life. 
The shell is lined with a membrane called the mantle. 
The mantle secretes the shell-material and adds to its size 
year by year. At the back, the edges of the mantle are 
united at three points, thus forming two openings known as 
siphons (sl'fons). Through one of these siphons water 



Figure 170. — Clam Showing Foot. 




186 


THE MOLLUSKS 


enters, carrying food and oxygen. Through the other the 
water passes out, carrying the waste from the body. 

Between the mantle and the body proper are four gills, 
which hang free in the shell cavity. The gills are filled with 
holes through which water passes. 

The foot, which is attached directly to the body proper, is 
that part of the clam hard to chew when it is eaten. v The foot 
and body form a solid mass that nearly fills the space be¬ 
tween the shells. 

The two valves of the clam shell are held together by 
means of strong muscles, attached to each shell. One of 

these, located in front of 
the body, is known as the 
anterior (front) adductor 
(ad-duk'ter) muscle; the 
second is just back of the 
body and is the posterior 
(back) adductor muscle. 
When these two muscles 
contract, the two valves 
are held tightly together. 
Before the live clam can be 
examined these two muscles have to be cut, as it closes its 
valves when handled. When the clam is dead, these muscles 
relax and the hinge forces the valves apart. It is not safe to 
eat clams and oysters that have died in their shells. 

When the two adductor muscles are cut free from the 
valves, a round or oval surface is seen which is marked off 
from the rest of the interior of the shell. These* areas 
are called muscle scars (Figure 171). 

When the empty clam shell is examined, it is found 
that the hinge, sometimes called the hinge ligament, is 
elastic. This is shown by compressing the two valves and 
seeing how promptly they open when the pressure is taken 
off. Where the two valves come in contact just beneath 



Figure 171. — Left Shell of Clam. 


Showing mantle and muscles. a.a., 
anterior adductor muscle; p.a., posterior 
adductor muscle. 





FOOD 


187 


the hinge ligament, a blunt projection of one shell fits into 
a depression in the other. These are called the hinge teeth. 


LABORATORY STUDY 

Live clams can be secured in the market during the school year. The 
dissection of the clam is too difficult, but the arrangement of the organs 
in the mantle cavity can be studied. The position of the adductor 
muscles, foot, gills, palps, heart, etc., should be observed. Examine a 
small portion of a gill under the microscope for cilia. A variety of 
shells of clams should be studied in which hinge, muscle scars, and hinge 
teeth are examined. Compare clam and snail shells. 



Digestive System. — The mouth, which is located under the 
anterior adductor muscle, leads through the short esophagus 
to the stomach. The in¬ 
testine winds through the __ ' ~~ 

foot region forming a loop, 
finally ascending and pass¬ 
ing through the peri¬ 
cardium and between the 
chambers of the heart it¬ 
self and opening into the 
upper siphon (Figure 172). 

Circulation is well de¬ 
veloped. 1 From the heart colorless blood is carried through 
arteries into smaller tubes, and returns, through veins, back 
to the heart. 

173. Locomotion. — The movements of the fresh-water 
mollusks are extremely slow. In the clam the foot is 
forced out of the shell by the blood, which flows into it 
and causes the foot to be greatly enlarged. Muscles attached 
to the shell and front of the foot contract and pull the shell 
forward over the extended foot. 


Figure 172. — Digestive Tube of Clam. 
m, mouth; s, stomach: i.c., intestine. 


1 The three-chambered heart lies in the dorsal region, near the hinge, in a 
little soft-walled chamber, the pericardium (per-i-kar'di-um: Greek peri, 
around; cardia, heart). 







188 


THE MOLLUSKS 


174. Food. — The food of the clam consists of microscopic 
plants and animals that are caught in a sticky fluid (mucus) 
on the gills, as the water passes through them. The food, to¬ 
gether with the mucus, is moved into the mouth by means of 
cilia. The mouth is simply an opening into the body and the 
cilia are on triangular flaps or lips (palps) on either side of 
the mouth. From the mouth food passes into the digestive 
canal, where the nutritious parts are absorbed (Figure 172). 

175. Respiration. — The clam, like other aquatic animals, 
gains its oxygen from the water and gives off carbon dioxide. 
A close inspection of the mantle shows the presence of blood 
vessels which are more numerous than in the gills. For 

this reason, the mantle is regarded 
as the main organ of respiration, 
although the gills also assist. 

176. Excretion. — The wastes 
of the body are absorbed by the 
kidneys and passed out into the 
water through the upper siphon. 

177. The Nervous System is 
not so well developed as in the 
crayfish. There are three groups 
of ganglia (nerve cells). One lo¬ 
cated far back in the body near 
the posterior adductor is called 
the visceral ganglion because it 

largely regulates the activities of the viscera (vis'se-ra), the 
internal organs of the body. Another in the foot region is 
called the pedal (pe'dal) ganglion, and regulates the move¬ 
ments of the foot. A third located in the region of the gullet 
(esophagus) is the cerebral ganglion, which regulates the 
activities of the part near the mouth. All these are con¬ 
nected by nerves. 

178. Life History. — In clams the sexes are distinct. 
Eggs formed in the ovaries of the female fuse with sperm 



Figure 173 . — Embryo of Clam. 


At this stage it becomes at¬ 
tached to the gills or fins of a 
fish. Here it remains for some 
weeks, gradually transforming 
into a clam. 





SNAILS 


189 



Figure 174 . — Snail. 

Notice the relation of the animal to its 
shell. The eyes are borne on the ends of 
the tentacles on the top of the head. 


cells from the males taken in with the water through the 
siphon. These sperm cells have reached the water through 
the upper siphon. Thousands of embryos form in the body 
of the female and develop 
into larvae in the outer 
gills, which thus become 
greatly distended. Later 
the larvae pass into the 
water through the upper 
siphon. ( 

The larvae of many 
fresh-water clams have 
hooks on their shells by 
means of which they are 
able to cling to the gills or body of a fish, where they live as 
parasites for several weeks. They absorb food from their 
host and are carried from one place to another and are thus 

scattered. After a few 
weeks they leave the host 
and settle down to lead 
an independent life. 

179. Snails. — Snails, 
having one valve, are 
called univalves as dis¬ 
tinguished from clams, 
oysters, etc., which are 
called bivalves because 
their shells are formed of 
two valves. The greater 
number of snails are ma¬ 
rine (live in salt water), 
although some live in 
fresh water and some on 
land. Snails have a broad 
foot which is used as a 



Figure 175 . — Our Common Pond Snail. 

Notice that they are able to creep along 
the surface of the water like a fly walking 
on the ceiling. They also have special 
paths running in various directions through 
the water. These paths are made of slime 
that the snail gives off. There is a mass 
of eggs attached to one of the plants. 
These eggs are orange color and deposited 
in a mass of jelly. 












190 


THE MOLLUSKS 


creeping disk. There is a head region provided with eyes 
and tentacles. The mouth of the snail is provided with a 
rasping structure known as the lingual 
ribbon (lm'gwal: Latin, lingua, tongue) by 
means of which it is able to cut and bore 
its way, even through rocks. Land snails 
by osmosis get oxygen from the air through 
the mantle, while water snails use gills and 
take their oxygen from the water. 

In the garden slug the shell when present 
is thin and affords small protection. 

180. Pond Snail. — The pond snail, 
gual Ribbon of a known by the scientific name of Physa, is 
kLrged)^ reatly 6n " Ver ^ common fresh-water ponds, where 
it lives among the water plants. It moves 
about by means of muscular movements in its broad foot. 
It is interesting to observe Physa from beneath as it creeps 
over the surface of glass and to note these contraction 
waves. As it 
moves through the 
water a trail of 
slime is left be¬ 
hind. If these 
snails are studied 
in a jar of water, 
some will be seen 
creeping along 
the surface, some 
slowly sinking to 
the bottom and 
others creeping up 
slirqe threads (Fig- Figure 1 77. —Snail Shells. 

ure 175). 

The pond snails live almost entirely on plants. Most of 
these plants are caught in the slime threads and both are 








SQUIDS, CUTTLE FISH, AND OCTOPI 


191 




Figure 178. — Soft-shelled Clam. 

Much prized as food. I.S., incurrent siphon ; E.S., excurrent siphon. 
Note the clam’s foot. 


then eaten. Snails also gnaw away the surface of the water 
plants with their rasp-like tongue (Figure 176). 

These snails lay eggs in jelly-like masses that stick to the 
leaves of plants. The 


jelly-mass protects the 
developing embryos and 
furnishes food to the 
young snails. As soon 
as the young of Physa 
are fully formed they 
escape from the jelly- 
mass and are able to care 
for themselves. 

181. Squids, Cuttle 
Fish, and Octopi belong 
to the Cephalopods (sef'a- 
lo-pods: Greek, kephale, 
head; pod , foot), the 

highest division of the mollusks. The nervous system is 
highly developed. The eye of the squid in particular is 
complex and more like the eye of vertebrates than of any 


Figure 179. — An Octopus or Devil¬ 
fish. 









192 


THE MOLLUSKS 


animal thus far considered. The mouth of cephalopods 
is surrounded with tentacles. 

A common squid, Sepia (se'pi-a), has ten arms or tentacles, 
two long and eight short. It moves itself forward rapidly 
by shooting out water from a siphon in the collar region. 
When pursued, the squid ejects an ink-like fluid which 
clouds the water, concealing it from its prey and facilitating 
its escape. 



It, like all other animals, begins as a single cell. 

Cuttle fishes are similar to squids, the marked differences 
being in the shape of fins, the form of the eyes, and the 
shape of the longer tentacles. 

The octopi are the largest members of the group. They 
have eight tentacles, which in some cases reach a length of 
thirty feet. The stories about the size and behavior of the 
octopi are often exaggerated. 

182 . Economic Importance of the Group. — Clams, 
scallops, oysters, and snails are used as food in all parts of 
the world. In this country, oysters are gathered in great 
abundance from Chesapeake Bay and other bays along the 
Atlantic Coast. 

The edible clams are of two kinds. The round clam, 
Venus mercenaria (Ve'nus mer-se-na'ri-a), is more generally 




ECONOMIC IMPORTANCE OF THE GROUP 193 



used as food, but the soft-shelled clam, Mya arenaria (mi'a 
ar-en-a'ri-a), is eaten extensively near the seashore. The 
soft-shelled clam has a long siphon which may be extended 
several inches beyond the valves (Figure 178). 

The scallop (skol'lup) is another mollusk that is eaten near 
the shore more extensively than elsewhere. This mollusk 
has but one adductor muscle, which is the edible portion. 


Figure 181. — Barnacles and Clams Growing on Oysters. 

Clams and oysters are raised artificially and regularly 
planted on natural feeding grounds. Care is taken to 
have such natural enemies as the starfish removed, and, in 
the case of oysters, brush and shell are added that they 
may fasten to these rather than sink to the bottom, where 
they become covered with mud. 

The culture of oysters and clams near the mouths of 
rivers contaminated with sewage is unsanitary, and dis¬ 
ease may be caused by eating such mollusks raw. This 
is one reason for the laws regulating the disposal of sewage, 
and for government inspection of the feeding grounds. 



194 


THE MOLLUSKS 


SUMMARY 

The parts of mollusks are not arranged in segments 
like the earthworms or crustaceans. The usual presence 
of a shell and mantle and the fact that the soft body is 
not divided into segments helps to distinguish a mollusk 
from any other animal. The microscopic food of the 
clam is caught in the mucus and carried by cilia to the 
mouth. The clams and oysters are valuable for food but 
should not be eaten if taken from water contaminated by 
disease germs. Mollusk beds should be protected from 
such contamination. 

QUESTIONS 

What are some of the common mollusks? Where do they live? 
How do they get their food? What ones are used for food by man? 

REFERENCES 

Brooks, The Oyster. 

Cambridge Natural History, Vol. III. 

Kellogg, The Shellfish Industries. 

Linville and Kelly, Zoology. 


PART II 


PLANT BIOLOGY 

CHAPTER XV 

THE LIFE OF FLOWERING PLANTS 

183. Introduction. — The plants that we all know and 
admire best are those that at some time in their lives produce 
beautiful flowers. These flowers, however, are only tem¬ 
porary structures which drop off as soon as their work is 
done. They are the special adaptations of the plant for 
producing more plants. The parts of the plant which have 
to do with its own life and well-being have adaptations too, 
many of which are as interesting as the flowers. 

These parts of a plant may be divided into two groups: 
those that are adapted to doing their work in the air, such 
as the leaves and the stem, and those which do their work 
in the soil, such as the roots and root hairs. In studying 
these parts of some of our familiar plants we shall give most 
attention to those structures which require explanation as to 
how each does its share in helping the whole plant to live. 

All these structures, the flower, the leaves, the stem, and 
the roots, are common to most plants. Each structure as¬ 
sumes its part in carrying on the life processes of the plant 
which could not live successfully without them all. A 
plant is an organism, and its several parts are organs or 
groups of organs (page 7). 

We thus begin our study of plants with their special 
adaptation for their work which is just the way that we began 
our study of animals. 


195 


196 


THE LIFE OF FLOWERING PLANTS 


In our study of flowering plants we can begin with any 
organ or with any stage in their life history. Many persons 
begin with the seed. In this book we shall begin with the 
flower. 

If the study of plants is begun in the fall, the nasturtium 
flower offers a good example of adaptations. You will 
notice that it has (1) a striking color in contrast with the 
foliage. This enables insects to see it readily. (2) It has 
an odor. This enables insects that are guided largely by 
the sense of smell to find it. (3) It has a long nectar spur 
on one side of the flower. This attracts the larger insects 
for the food they can get. (4) The lower petals have an 
inner fringe which retards the crawling insects that are trying 
to get the nectar. (5) The upper petals project over the 
other parts of the flower. This keeps the rain from running 
down the nectar spur and prevents the pollen from becoming 
wet. (6) The lower petals have stripes that lead to the 
opening of the nectar spur. This indicates the direction 
that insects should travel to find the opening quickly. 
(7) The anthers mature at different times. This insures 
a supply of pollen on different days so that some of the pollen 
is in condition to use, even if some has been spoiled by un¬ 
favorable weather. (8) The anthers and stigma mature 
at different times so that the pollen cannot-get on its own 
stigma. This ensures hardier seeds by preventing inbreed¬ 
ing. There are at least eight ways in which the nasturtium 
flower is adapted to the visits of insects and to the protection 
of its pollen and nectar. There are many other aspects of 
the study of flowers as interesting as the study of adaptation, 
some of which will be mentioned later. 

LABORATORY STUDY OF A NASTURTIUM 

Provide each pupil with a nasturtium flower. 

Draw the flower, and label the parts as follows : (1) sepals, the outer¬ 
most, greenish parts; (2) petals, the colored, larger parts; (3) stamens, 



Charles Edwin Bessey was born in Milton Township, Wayne 
County, Ohio, May 21, 1845, and died at Lincoln, Nebraska, 
February 25; 1912. 

He was educated in the country schools and academy, and at 
the Michigan Agricultural College, from which he graduated in 
1869. In February, 1870, he began his duties as Professor of 
Botany at the Iowa State College at Ames, Iowa. In addition to 
botany, he taught zoology and entomology for the larger portion 
of the fifteen years that he remained at that institution. He as¬ 
sumed the professorship of botany at the University of Nebraska 
in November, 1884, a position held by him until his death. 

His greatest contributions to botany are: the introduction of 
the laboratory method in teaching the science ; his enrichment 
of the whole field of botany by teaching many new aspects of the 
subject; and his profound influence upon students and future 
investigators. 








































































































































, 












* 



























































































































INTRODUCTION 


197 


the slender parts inside the petals; (4) pistil, the central part of the 
flower; (5) spur, the projection on one of the sepals; (6) peduncle, the 
flower stalk. 

How many sepals are there ? Are they all the same size and shape ? 
How many petals are there? Are they all the same size and shape? 
Have they all furrows, or streaks of color leading to the base of the 
flower? If not, which ones have one or the other? Which ones have 
a hairy fringe on the inside ? Do the hairs all point in the same direc¬ 
tion? Open the end of the spur and taste the liquid. Describe the 
taste. 

How many stamens are there? Draw one and label (1) filament, 
the slender, stalk-like part; (2) anther, the enlarged top which contains 
yellow, dust-like particles, the pollen. If possible, examine pollen 
grains with a microscope. Describe them. 

Draw the pistil. Label (1) stigma, the top portion; (2) style, the 
slender part below the stigma; (3) ovary, the enlarged base. Examine 
the stigma with a hand lens. Does it appear sticky? Can you see 
pollen grains on it? Cut across the ovary. How many chambers 
has it? How many ovules (small, white bodies) are in each chamber? 
Draw and label. 

Examine a nasturtium blossom that has stood in water till it has 
withered. What parts of the flower have dried up? Which ones 
have fallen off ? What parts remain ? What changes have taken place 
in those that are left ? 

SUGGESTIONS FOR HOME WORK 

Compare any blossoms you have at home with the nasturtium 
(geranium is a good one). Do you see any indications of irregularity 
in the geranium ? of a spur ? of colors or furrows on the petals ? Ex¬ 
amine other flowers in the same way — apple, violet, lilac, chickweed, 
etc. Make notes and sketches of # what you find out for yourself, and 
of questions that occur to you. 

In comparing the flower with the remarks about it in 
section 183, you will note that different parts of the flower 
have special names. Furthermore, you will find that many 
other flowers have all or some of the same parts. In order 
to talk about them intelligently, therefore, it will be necessary 
to know more about the parts of flowers, their names and 
their relations to one another. 


198 


THE LIFE OF FLOWERING PLANTS 



184. Parts of a Flower Found in Nasturtium. — Sepals 
(Latin, separ, separate). — These are greenish pointed leaf¬ 
like parts on the outside of the flower. Together they make 
up the calyx (Greek, kalyx, cover), which protects the other 

parts, at least while they 
are in the bud, from in¬ 
sects, cold, rain, etc. One 
of the sepals has a spur in 
the bottom of which is a 
drop of nectar. 

Petals (Greek, petalon, 
leaf). — The larger parts, 
more showy because more 
brightly colored, are 
petals, which taken to¬ 
gether make up the corolla 
(Latin, corolla, crown). 

Stamens (Latin, sto, 
stand). — These are the 
slender organs which sur¬ 
round the most central 
portion of the flower. 
The stamen has two 
parts, the filament or 
stalk, and the anther or 
box at the top, which 
Figure 182. —Flower of Nasturtium. con tains the pollen. 

b whole flower. A, sepal ; B, petal ; C, PiM. — The central 
stamens : D, pistil; E, spur. 2, petals. .. „ .. 

portion of the nasturtium 

is the pistil, made up of three parts. At the top is (1) the 
stigma (Greek, stigma, point); below it (2) the style (Greek, 
stylos, pillar) which connects it with the lowest part, (3) the 
ovary (Latin, ovum, egg). 

The sepals and the petals are sometimes spoken of as 
floral envelopes or as accessory parts, in distinction to the 





THE LILY 


199 




Figure 184. — Pistil and 
Stamen of Nasturtium. 

1. A, 3-parted stigma; 
B, style ; C, 3-parted ovary ; 
D, receptacle ; E, peduncle. 

2. A, anther, with pollen ; 
B, filament. 


Figure 183. — Flower of Nasturtium 
with Petals Removed. 

stamens and the pistil, the essential 
parts. Only the latter are neces¬ 
sary for the production of seeds. 

The nasturtium is a perfect flower 
because it has the parts necessary 
for the production of seeds, and it 
is a complete flower because it has 
also the accessory parts. 

185. Th e Lily .—When the study 
of flowers is begun in the spring, 
the lily affords a good example. Let us see what adapta¬ 
tions it has. (1) It is a large showy flower. Insects can 
see it easily. (2) It has a strong odor, enabling insects to 
locate it by smell. (3) It has a long pistil which protrudes 
beyond the other parts, affording a good place for insects to 
alight. (4) It has long stamens so arranged that when an 
insect alights on the pistil, it is sure to become dusted with 
the pollen from them. (5) Its pistil has a sticky enlarged 
end which is almost sure to catch pollen grains from the 
insect’s body. (6) It has nectar glands around the bases 
of the stamens which yield food for the insects. (7) It has 


















200 


THE LIFE OF FLOWERING PLANTS 


furrows in the petals leading to the nectar glands. This 
helps the insect to find the nectar. (8) The stamens bear 

the pollen on their outer 
surfaces, a safeguard 
against self-pollination. 
(See p. 211.) 

186. Parts of a Lily. 
— In speaking of the 
adaptations of a lily, sev¬ 
eral terms have been used 
which need to be ex¬ 
plained 'further, as the 
parts which they repre¬ 
sent are found in most 
flowers. The pistil is 
the central organ of the 
flower. It has three 
parts, (1) the expanded, sticky stigma (Greek, stigma, point) 
at the top, (2) the style (Greek, stylos, 
pillar), the long, slender connecting por¬ 
tion, and (3) the ovary (Latin, ovum, egg), 
the expanded base. Inside the ovary are 
the ovules which contain the egg cells from 
each of which an embryo plant will de¬ 
velop if it becomes fertilized. The part 
of the ovary to which the ovules are 
attached and through which they get 
their food is the placenta. The stamens 
(Latin, sto, stand) are the parts of the 
flower outside of the pistil and surround¬ 
ing it. Each stamen consists of a slender 
stalk, the filament, and an anther, the part ^’ ra ^ he ^’ fluent* 1 
which contains the pollen. The stamens 
and the pistil make up the essential parts of the flower, for 
with them alone, seeds can be produced. Around the outside 



Figure 186. — Sta¬ 
men of Lily. 



Figure 185. — Flower of Lily. 

A , divisions of perianth ; B, stamens ; 
C, pistil. 












PARTS OF A LILY 


201 


of these organs are the colored parts which together form the 
perianth of the flower (Greek, peri, around, anthos, a flower). 
In the lily the perianth consists of six parts of the same color, 
size, and shape. Because of the even size and regular shape of 
the parts of the perianth of the lily, we speak of it as a regular 
flower. The perianth is an accessory part of the flower, for 
seeds can be made without it, the stamens and the pistil 
being the only essential parts. Any flower which has all 
the parts which a flower may have is called a complete flower. 
If it has both stamens and pistil, the essential parts, it is 
called a perfect flower. * 

LABORATORY STUDY OF A LILY 

Each pupil is to be provided with a lily. 

Draw the flower and label the parts as follows : (1) perianth, the large 
outer parts taken together; (2) stamens, the slender parts bearing the 
yellow, dust-like pollen; (3) pistil, the central part of the flower; 
(4) peduncle, the flower stalk. 

How many divisions has the perianth ? Are they all the same shape, 
size, and color ? Have they all furrows or markings leading to the base 
of the flower ? Are there drops of nectar, a sweet substance at the base 
of the stamens? 

itHow many stamens are there? Draw one and label (1) filament, 
the stalk-like part; (2) anther , the enlarged top which bears the pollen; 
if possible, examine the pollen grains with a microscope. 

Draw the pistil and label (1) stigma, the enlarged upper end; (2) style, 
the slender portion below the stigma; (3) ovary, the enlarged base. 
How many lobes has the stigma? Is it sticky? Are there pollen 
grains upon it ? 

Cut across the ovary. How many chambers has it ? Are there few 
or many ovules (small, white bodies) in each? Draw. Label the parts 
to which the ovules are attached, placenta. 

Let a lily stand in water till it withers. What parts have dried up ? 
What other changes have taken place? Cut across the ovary. Com¬ 
pare with your drawing and tell what differences you see. Draw the 
ovary as it now appears. 

Besides the four sets of parts found in nasturtium flowers, 
other parts will be found in certain flowers, the receptacle, 


202 


THE LIFE OF FLOWERING PLANTS 


for example, the expanded top of the stalk on which the 
floral organs are placed. This is sometimes oval as in 
buttercups, or large and fleshy as in strawberries, or hollow 
as in the rose, where the pistils arise from its inner surface. 
The crown is a projection growing from the surface of a petal 
as in narcissus. The spur already mentioned is another 
modification of a petal or a sepal. Violets, snapdragons, 
toad flax, and larkspur have spurs. Nectar glands, usually 
found near the base of a flower, are commonly found in those 
flowers which are adapted to attract insects. 

187. What Is a Flower ? — It has bekn decided that a flower 
is simply a modified branch, the parts of the flower being 
highly specialized or modified leaves. Some flowers show 
this plainly at all times, and others show it under certain 
conditions. 

188. Uses of the Parts of a Flower. — The sepals are 
adaptations for the protection of the inner organs while they 
are developing, and the petals are adaptations for the pur¬ 
pose of attracting insects to distribute pollen. Sometimes 
one set of these organs is lacking and sometimes the other, 
giving us asepalous or apetalous flowers as the case may be. 
Very often, sepals are colored and serve the purpose of 
petals, another adaptation. The receptacle serves as the 
place of attachment for the other parts of the flower. 

Stamens . — These produce the pollen without which 
seed cannot be formed. Concerning the ways in which they 
open, the kind of pollen they bear, their adaptations for 
getting it to the pistil of another flower and (usually) for 
keeping it from its own, enough has been discovered to fur¬ 
nish text for a whole book, although many flowers have 
not yet been studied at all. Many of these facts can be 
observed by any boy or girl with keen eyes. To be on the 
lookout for new facts will give zest to the study of botany. 

Pistil. — In the ovary of the pistil are found the ovules 
which will become seeds under favorable conditions (see 


OTHER TERMS USED IN DESCRIBING FLOWERS 203 


sections on Pollination and Fertilization). The stigma and 
the style are parts which help to fulfill these conditions. 
The position of the ovules in the ovary, the adaptations of 
the stigma for catching and holding pollen, the position of 
the stamens with reference to it, the adaptations of the 
pistil for the passage of the pollen tubes through it, — all 
these furnish the basis for a fascinating study which can be 
carried on by anyone who 
has access to flowers, and 
who has time and pa¬ 
tience. 

When a flower has fin¬ 
ished its work, namely to 
secure the fertilization of 
its ovules, its showy parts 
wither, if it had any, and 
the fruit begins to form. 

Usually it is only the 
ovary which enters into 
the fruit; but in some 
cases, the receptacle is in¬ 
cluded, and in others the 
calyx remains unchanged. 

The biologist who is interested chiefly in adaptations of 
flowers and in their relations to insects will not need many 
scientific terms for his work. Persons who have occasion 
to classify plants, however, need to know a few more terms. 
Farmers and gardeners need to know other facts about 
flowers. For them still other terms are necessary. 

189. Other Terms Used in Describing Flowers. — Flowers 
which lack any one of the four sets of parts which the nas¬ 
turtium has are incomplete flowers. The apetalous flowers 
of the grasses are examples. 

Imperfect flowers bear only one of the essential parts of 
a flower; so we find staminate flowers, bearing stamens only, 





204 


THE LIFE OF FLOWERING PLANTS 



like the tassel of the corn, and pistillate flowers, bearing 
pistils only, like the young ear of corn with its long silks 
(pistils). Some plants, like the corn, bear both kinds on 
the same plant, even though in separate flowers. In this 
case we say the plant is monoecious (mo-ne'shus: Greek, 

monos, one ; oikos, house). 
Other plants have only 
staminate or only pistil¬ 
late flowers like the wil¬ 
low and ash which we 
call dioecious (dl-e'shiis: 
Greek di, two; oikos, 
house) plants. 

Regular flowers are 
those which have all the 
parts of a kind the same 
size and shape. Such a 
flower is the lily. 

Irregular flowers have 
many variations, but they 
are all alike in having the 
parts of the same set of 
different size and shape. 
The bean flower, the nas¬ 
turtium (see Figure 182), 
and the violet illustrate 
this. 

Double flowers are those 
in which the stamens or 
part of them have turned to petals. How would this affect 
the production of seed? Cleistogamous flowers (klis-tog'a- 
mus : Greek, kleistos, closed; gamos, marriage) are those which 
some plants form for the sole purpose of producing seeds 
without the help of insects. They usually grow below the 
surface of the ground, have no petals, have only one or two 


Figure 188 . — Pistillate Flowers of 
Corn. 

Immature grains, each of which has a 
long, green style, the “silk.” The husks 
are modified leaves. 



OTHER TERMS USED IN DESCRIBING FLOWERS 205 


stamens, and they never open. The sepals protect them, the 
parts are so arranged that none of the pollen is wasted, and 
the number of seeds produced is even larger than in an ordi¬ 
nary flower. Violets make use of this kind of flower after 
the others have finished blooming. 



Figure 189. — Violet Plant with Cleistogamous Flowers. 


SUGGESTIONS FOR DEMONSTRATION BY TEACHER 

Direct the observations of pupils in studying the flowers of a dande¬ 
lion. Note old (mature) flowers on the outer part of the head, and 
young (immature) flowers in the inner part. Note the notches at the 
end of the long corolla. What does this indicate? Note the number 
of filaments, and the anthers united in a ring, opening on the inside. 
Call attention to the fact that the anthers mature before the pistil does. 






206 


THE LIFE OF FLOWERING PLANTS 


Show how the pistil, with its stigmatic surfaces pressed tightly together, 
pushes up through the pollen which fills the tube, becoming covered on 
the outside. Show mature pistil with expanded stigma. If possible 
show dandelions with insects on them. What 
are the insects doing? What happens to the 
pollen ? 

Pollen grains. — Place a few, preferably large 
ones, on a slide; cover with 5 per cent sugar 
solution; put under a bell jar and set in a warm 
place for half an hour. Then add a cover glass 
and examine for pollen tubes. Examinations 
may be repeated at intervals for a number of 
hours. 

Carefully split the style of a large flower, like a 
lily, noting the passage in the middle for the pollen 
Figure 190. — Disk tubes. If the pistil has not a tubular center, 
Flower of Daisy. what is the character of the tissue in the center? 



190. Composite Flowers. — These flowers are closely 
crowded or grouped into a head, on a common receptacle. 
Such is the dandelion or the daisy, each 
group being commonly called a flower. 

Two lands of flowers are to be found in 
these heads, tubular flowers, that is, with 
the corolla a tube, and strap-shaped flowers 
in which the corolla is long and slender. 

Some composite flowers, like the dande¬ 
lion, have only the strap-shaped, and 
others, like the thistle, only the tubular 
kind. Still others, like the common daisy 
and the sunflower, have both kinds. In 
the daisy, the tubular flowers, found only 
in the middle, are called disk flowers. 

These make up the yellow part of the 
group. Outside of them are the white 
strap-shaped kind, known as the ray 
flowers. In the sunflower the disk flowers are brown, and 
the ray flowers yellow. Many other combinations occur. 



Figure 191. — Ray 
Flower of Daisy. 









COMPOSITE FLOWERS 


207 


Dandelion flowers show many adaptations. The stamens 
are joined in a ring with the anthers opening on the inside of 
the ring. The anthers mature their 
pollen before the pistil of that flower 
is ready for pollen. The pistil, with its 
stigmatic surfaces pressed tightly to¬ 
gether, pushes up through the mass of 
pollen filling the tube, becoming cov¬ 
ered on the outside. Insects crawling 
over the head drag some of these pollen 
grains to pistils which are mature. When 
the pistil of any one flower, expands, its 
own pollen is not likely to get on it. 

The closely crowded flowers, the ar¬ 
rangement of their parts, the bright 
color, the abundant pollen and the cer¬ 
tainty of cross-pollination are adapta¬ 
tions which make the dandelion one of 
the most successful of plants. 

The composites as a whole show more 
adaptations than other flowers, so we 
find among them those which are of 
most interest to the scientist and those 
which are of greatest annoyance to the 
farmer, namely, wild carrot, paint-brush, 
burdock, and thistles of all kinds. They 
are most successfully fought by not giv¬ 
ing them opportunity to blossom and 
form fruit. In some cases, roots as well 
as seeds serve to propagate plants. Tap¬ 
roots (page 250), characteristic of some 
plants, help them to maintain them¬ 
selves under unfavorable conditions, 
and rhizomes (page 334) help the plants 
which have them to spread. 


f \ 

4-A 

" ■ J 


1 

|C|-—c | 

- hU 

ill 

1 

\i 

111—~ D 

|J-: E ... 

1 

1 


f 

a\ 

/ ,. agl 


m 


4 — c 

I 


Figure 192. — Flower 
and Fruit of Dan¬ 
delion. 

Upper figure, A , 
strap-shaped corolla ; 
B, stigma; C, style, 
covered with pollen 
grains; D, stamens 
united by their anthers; 
E, filaments; F, pap¬ 
pus ; G, akene. 

Lower figure, A, re¬ 
mains of flower; B, 
pappus; C, akene. 






208 


THE LIFE OF FLOWERING PLANTS 


HOME WORK 

Examine vacant lots, waste spots, and gardens for weeds. How many 
of them are composites? 

Study flowers in vacant lots, and record the results, using the follow¬ 
ing table as a guide. 



COROLLA 

Regular 

Corolla 

Irregular 

Corolla 

Lacking 

j « 

II 

sj 

V 

£2 

Pistils only 

in a Flower 

Flower 

Perfect 

Geranium . . . 

Castor bean. . . 

Salvia. 

Nasturtium . . . 

Pansy. 

Etc. 

X 

X 

X 




X 


191. Pollination. — When insects go to a plant they gener¬ 
ally have a definite errand, namely, to get pollen or nectar from 
it. As shown by the nasturtium, or the lily, they are helped 
in this by adaptations of the flower. At the same time, the 
flower has other adaptations which cause the insect to become 
covered with pollen as it leaves the flower, and still other 
adaptations which bring it about that when the insect 
enters a flower, some of the pollen from the flower last visited 
is left on the stigma of the one which it is entering. 

Pollination is only the first step in the production of 
seed. Before we can understand the use of pollination, we 
must understand the structure of the pollen grain. 

Pollen grains present the greatest variety in size, structure, 
and markings, but all have some features in common. They 
all have a double coat or covering, the outer of which is 
thin in places. When a pollen grain is caught on a sticky 
stigma, it soon sprouts; that is, the inner coat pushes out 
through the thin places in the outer coat, producing a tube. 



















POLLINATION 


209 


This contains the protoplasm of the pollen grain, and two 
nuclei, one of which, the sperm nucleus, will join with that 
found in the ovule, the egg nucleus, to start the new plant 
formed in the seed. 

The pollen tube and the style both show adaptations. The 
style is either tubular, affording a path for the pollen tube, 



A, whole flower. Note the platform where the insect alights. 

or it is composed of cells very loosely packed, allowing the 
tube t6 pass through it readily. The adaptations of the 
tube are its ability to absorb food from the tissues through 
which it passes, and to find the micropylar opening of the 
ovule. 









210 THE LIFE OF FLOWERING PLANTS 

Cross-Pollination. — Reference has been made to the 
fact that pollen is necessary for the formation of seeds, and that 

in most cases it is the 
pollen of some other plant 
of the same kind that is 
used. When the pollen 
of one flower is trans¬ 
ferred to the stigma of 
another of the same kind, 
the process is known as 
cross-pollination. On the 
other hand, when a stigma 
gets pollen from the sta¬ 
mens of its own flowers it 
is said to be self-polli¬ 
nated. The distribution 
of pollen is accomplished 
by insects and by wind more than by other agents. Pollen 
that is to be scattered by wind has two adaptations: (1) it 
is very abundant, for much of it is 
light, that it may be easily carried. 

The pollen of pines which is so 
abundant as to cause the so-called 
“sulphur showers” in the spring 
illustrates this, and the pollen of 
grasses which is extremely light 
illustrates the other fact. Plants 
that are wind-pollinated usually 
lack odor and color and floral en¬ 
velopes (accessory parts), but they 
have adaptations in the stigmas, 
which are either plumy or feathery 
or broad and sticky, the better to 
catch and hold the pollen grains 
brought to them by the wind. 


sure to be lost; (2) it is 



Figure 195.— Pollen Grain 
Sprouted. 


The upper nuclei are male or 
generative nuclei. * 



Figure 194. — Salvia. 

A , stamens mature ; B, pistil mature; 
C, flower after pollination. 







FERTILIZATION 


211 


Seeds formed as a result of cross¬ 
pollination produce more vigorous 
plants than those which grow from 
seeds in self-pollinated flowers. 

Self-Pollination. — Some flowers, 
like the cleistogamous flowers of the 
violet, are arranged with a view 
to securing self-pollination. Most 
flowers, on the other hand, have 
adaptations to prevent it. One of 
these is bearing unisexual flowers 
only, pistillate and staminate flowers, 
on different plants as the willow does. 

Another is having pistil and stamens 
mature at different times (dandelion, 
see p. 207); and a third is having stamens and pistils of 
different lengths. When an insect visits such a flower, one 

part of its body is apt to come 
into contact with the stamens 
and another with the pistil. 
For example in the primrose, 
an insect which gets pollen 
from short stamens on its 
body in one flower leaves it 
on the short stigma of an¬ 
other flower. 

192. Fertilization. — The 
union of the pollen nucleus 
with the nucleus of the egg 
cell is called fertilization. 
Without it, the ovule never 
develops into a seed. (Look 
in pea or bean pods for unfertilized ovules; in the seed- 
case of an apple; on an ear of corn.) 

Successful fertilization depends much on thorough pollina- 



Figure 197. — Pollen Tube, En¬ 
larged. 

A, tube ; B, loose cells of style. 



Figure 196. — Pollen 
Grains Sprouting and 
Growing through 
Style. 












212 


THE LIFE OF FLOWERING PLANTS 


tion. For this reason farmers and gardeners should know 
the habits of the insects which pollinate flowers and the best 
way to plant certain crops to secure the results desired. 

193. How Fertilization Is Accomplished. — When pollen 
grains fall on a stigma they are held there by a sticky sub¬ 
stance or by projections, 
and each soon puts forth 
a tube as already ex¬ 
plained. The tube makes 
its way through the style 
either by means of a 
channel which traverses 
it or by making a path for 
itself through the loose 
tissue of which styles 
without channels are 
composed. The nuclei 
are always near the end 
of the tube, which may 
become very long com¬ 
pared to the size of the 
grain which produced it. 
(See Figure 195.) When 
it reaches the ovary it 
A , pollen tube ; B, micropyle ; C, outer turns towards an ovule 
integument ; D, inner integument ; E, em- which it enters usually 
C ’ fSmale throu S h the micropylar 
opening. When the tip 
of the tube containing the male nucleus touches the egg 
cell in the embryo sac, it bursts, and its nucleus unites 
with that of the egg cell, completing the act of fertilization. 
The ovule at the time of fertilization consists of a mass of 
tissue known as nucellus (Latin, nucella, small nut), which is 
enclosed by an outer and an inner integument (Latin, in, 
upon, tego, cover) except at one point, the micropylar open- 



Ovule in Act of Fertilization. 








INFLORESCENCE 


213 



ing. Imbedded in the nucellus is the embryo sac containing 
the egg cell which, if fertilized, will develop into a new plant. 
The ovule is attached to the ovary by a stalk called the funicle 
(Latin, funiculus , little rope) through which it receives food 
for its growth and de¬ 
velopment. 

As soon as the egg cell 
is fertilized it begins to 
divide, forming the new 
plant. At the same time 
other changes take place 
which result in the forma¬ 
tion of a seed. (See page 
219.) 

In the early days of 
the study of botany, per¬ 
sons were interested more 
in describing flowers mi¬ 
nutely and in classifying 
them than in learning 
about how they lived. 

Although the latter is 
now of greater interest, 
we still need many of the 
terms formerly used to 
describe the plants in 
order to read about them 
intelligently. For this 
reason, the ones most 
commonly used are given in the text or in references. 

194. Inflorescence. — Flowers that grow at the end of a 
separate stalk, like the common blue violet, tulip, daffodil, 
waterlily, and hepatica, are solitary flowers. This term is 
used also for the single flowers which spring one from the 
axil of each leaf as in pimpernel. As a rule, solitary flowers 


Figure 199. — Umbel. 

A flower cluster in which the pedicels 
arise from a central point. If the pedicels 
have the same length, the cluster is globu¬ 
lar, as in the milkweed. If the outer ones 
are longer, the cluster is flat, as in the 
wild parsnip. 





214 


THE LIFE OF FLOWERING PLANTS 



are larger and more showy than those which are arranged 
in clusters. 

The more common flower clusters can be identified by 
reference to the illustrations and to the explanations accom¬ 
panying them. Note that the flowers in a cluster are, in 

general, smaller or less 
conspicuous in color than 
are the solitary ones. 

Raceme .—This is a stem 
which bears flowers on 
both sides or spirally, each 
flower having a bract or 
reduced leaf at its base. 
The flowers may all hang 
from one side of the stem 
as in lily-of-the-valley or 
currant. 

Compound Raceme. — 
Here each pedicel branches 
regularly, as false Solo¬ 
mon’s seal. 

Thyrse. — This is a com¬ 
pact panicle forming an 
oval or pyramidal cluster, 
as bunch of grapes, lilac, 
horse-chestnut blossoms. 

Head .—This is a raceme 
in which the axis is very 
much flattened, or much 
rounded, as clover. 

Corymb. — This is an inflorescence in which the lower 
pedicels are longer, forming a flat-topped cluster, as haw¬ 
thorn. How does this cluster differ from the umbel of the 
wild parsnip in appearance and in structure ? 

In forget-me-not, hound’s tongue, and heliotrope, only 


Figure 200. — Compound Umbel of 
Wild Carrot. 

Note the fly which in crawling around 
is distributing pollen. 




INFLORESCENCE 


215 




Figure 201. — Compound Umbel of Wild 
Parsnip. 

Note the maturing fruit. 


Figure 203. — Panicle. 

A raceme in which the .branching is 
somewhat irregular, and the branchlets 
long, as head of oats or panicle of grass. 


Figure 202.— Cyme of Chickweed. 

A cyme is a flower cluster in which the 
■ terminal flower opens first (.4). Next in 
order, the terminal flower on each of the 
two axillary branches arising below it ( B ). 
Third in order, four flowers, one on each 
apex of the two branches arising from the 
axis of each flower of the second series (C). 
What does D represent ? How many will 
there be ? 


Figure 204. — Compound Cyme 
of Elder. 












216 


THE LIFE OF FLOWERING PLANTS 




one axillary branch arises below 
the terminal flower each time, all 
on the same side. 

In a raceme, spike, panicle, and 
head, the axis may go on growing 
and producing flowers during an 
indefinite period. 

In solitary flowers only one is 
ever produced on a peduncle; and 
in a cyme only the 
terminal fl6wer is 
ever produced on 
any one branch. 

The first group 
is known as in¬ 
determinate inflo¬ 
rescence and the 
second as determi¬ 
nate. 

Indeterminate 
inflorescence has 
its oldest flowers 
on the lower part 
of the axis (ra¬ 
ceme, spike, head) 
or on the outside 
of the cluster (corymb, umbel). The order 
of blossoming is centripetal. 

In the cyme the central flower is the oldest, 
producing others farther away with each 
branching, the order being centrifugal. 

195. Economic Value of Flowers. — Many 
plants are cultivated for the pleasure their 
flowers give us. Our use of them for pleasure 
very often defeats the object for which they 


Figure 205. — Spike. 

A raceme in which the flowers 
have very short pedicels or 
none, as plantain, Figure 206. 


Figure 206. 

A, region of 
mature pistils; 

B, region of ma¬ 
ture stamens; 

C, region of ma¬ 
turing fruit; 

D, region of ripe 
fruit. 







ECONOMIC VALUE OF FLOWERS 


217 


grow, from Nature’s standpoint, for they do not have a 
chance to develop seeds. 

Cauliflower and Brussels sprouts, the buds of which are 
used as food, are the most familiar examples of the use of 
flowers for this purpose. 

A few have been used for medicine, though not so much 
now as formerly. Among them may be mentioned dande¬ 
lion, the elder, the mullein, and camomile. 

Saffron, a yellow coloring matter, is obtained from the 
stigmas of the saffron crocus. 

SUGGESTIONS FOR HOME WORK 

As soon as flowers appear observe them closely and note which have 
many insect visitors and which have few or none. Fill out a report as 
suggested below and add any points which interest you besides those 
mentioned. 



Color Conspicuous 

Color Not Conspicuous 

Odor Strong 

Odor Not Strong 

Nectar Abundant 

Nectar Not Abundant 

Insects Many 

Insects Few 

Etc. 

Sweet Pea . 
Dandelion . 
Hepatica . 
Buttercup . 











Examine florists’ and gardeners’ catalogues, and note the plants the 
flowers of which are used as food and for ornament. Read about the 
use of hops and the process of raising and harvesting them. 


SUMMARY 

The flower is the part of the plant that produces fruit 
containing seeds for a new generation of plants. The 
essential parts of a flower are the stamens and the pistil, 



















218 


THE LIFE OF FLOWERING PLANTS 


which may not be in the same flower or even on the same 
plant. Other parts are merely accessory, being found in 
those flowers which depend on insects' for cross-pollination. 
Large, showy flowers are not grouped; but small, incon¬ 
spicuous ones are, to attract insects. Pollen which is dis¬ 
tributed by wind is very light and very abundant. Stigmas 
which depend on wind for pollination are plumy or sticky or 
both. Fertilization of the egg cell in the ovule is accom¬ 
plished when the sperm nucleus in the pollen, grain unites 
with that of the egg cell. A flower may be defined as a 
device to secure pollination. 

QUESTIONS 

Into what two groups may the organs of a plant be divided ? What 
organs are in the first group? What in the second? Name all the 
parts that a flower may have. Tell the use of each part. What are 
some of the adaptations of flowers that attract insects to them ? What 
peculiarities have flowers that are pollinated by the wind? What 
is fertilization? 

REFERENCES 

Bessey, College Botany, page 285; pages 302-313; 321-324. 

Snyder, General Science, pages 200, 201. 

Bergen, Foundations of Botany, 186-216. 

Conn, Biology, page 118. 

Bergen and Caldwell, Practical Botany, pages 104-135. 

Gibson, Sharp Eyes, page 115. 

Coulter, Plant Life and Plant Uses, page 58; pages 258-321. 


CHAPTER XVI 


THE SEED AND THE SEEDLING 

196. From Ovule to Seed. — At the time of fertilization, 
an ovule consists of a mass of tissue ( nucellus ) in which is em¬ 
bedded the embryo sac. The embryo sac contains an egg 
cell which, if fertilized by a nucleus from the pollen tube, 
will become a young bean plant (embryo). The ovule is 
covered by two coats ( integuments ) which do not quite meet 
at one end, leaving an opening, the 
micropyle (ml'kro-pll: Greek, micro, 
small; pyle, gate), a small door 
through which the pollen tube usually 
enters. It is attached to the wall of 
the ovary (placenta, see § 184) by a 
stalk (funicle, see § 193) through 
which it gets its nourishment. 

In developing into a seed several 
changes occur. (1) The integuments 
become firm and hard, the outer 
forming the testa. (2) The egg cell 
divides, forming the embryo. (3) The embryo sac is replaced 
by two cotyledons (kot-y-le'don: Greek, kotyledon, socket) 
which contain food for the embryo. (4) The micropyle be¬ 
comes smaller and almost closes. (5) The funicle drops off, 
leaving a scar on the bean seed, the hilum (hl'lum: Latin, 
hilum, a little body). 

197. Adaptations of the Seed. — The bean seed is the plant's 
way of providing for a new bean plant. It is adapted to 
fulfill that purpose in the following ways. (1) A ripe seed 

219 



Figure 207. — Bean Seed 
Showing Parts. 




220 THE SEED AND THE SEEDLING 

contains a young plant well started. (2) It can resume 
growth soon after being formed, or it can remain dormant 
for years. This might prevent total loss of seed. (3) It is 
surrounded by a hard testa which prevents the embryo from 
drying out during a long resting period. This enables it to 
remain viable (Latin, vita, life) for many years. (4) It can 
absorb water slowly through the micropyle when covered 
with moist earth. This softens the testa and causes the 

cotyledons to swell, help¬ 
ing to release the embryo. 
(5) The cotyledons con¬ 
tain food for the young 
plant till it can make its 
own. This insures fapid 
growth in the early 
stages, an advantage in 
competition with other 
seedlings. 

198. Growth of the 
Bean Embryo. — When 
the embryo resumes 
growth after a resting 
period, the root breaks 
out of the testa first. 
This is an adaptation, 
for it at once begins to 
absorb water needed for further growth and soon becomes 
firmly imbedded in the soil. The second adaptation is the 
curving of the hypocotyl (hy-po-kot'd: Greek, hypo, 
beneath; kotyle, cavity). This forms a loop on top of 
which is a hard portion, the peg. The hypocotyl grows 
rapidly, causing the arch of the loop to turn from side to 
side, pushing the particles of soil apart and working its way 
to the surface. Then the cotyledons are pulled up as the 
arch straightens. Finally, further growth of the hypocotyl 



Figure 208. — Seeds of Bean and Pea. 

Upper, split, showing embryo. (Only 
the part showing the embryo was saved.) 
Lower, whole, showing markings. A, em¬ 
bryo ; B, plumule; C, root; D, hilum; 
E, micropyle; F, embryo; G, hilum; 
H, micropyle. 



GROWTH OF THE BEAN EMBRYO 


221 


causes the cotyledons to spread apart, exposing the plumule 
(plum'ul: Latin, plumula , feather) to the air and light. At 
the same time the cotyledons begin to turn green, thus 
serving as leaves till the leaves of the plumule have developed. 
So the plumule is protected and given a chance to grow under 
good conditions. As soon as the food in the cotyledons is 
absorbed by the young plant, they shrivel and drop off. 



Left, root free; center, root branched, hypocotyl developed and show¬ 
ing the arch, cotyledons split apart, and plumule; right, young bean plant 
showing shriveled cotyledons, and first true leaves. 


The young bean plant is known as a seedling, while it is 
dependent on the store of food in the seed. 

In the course of a few weeks a bean plant is large enough to 
produce blossoms which develop into pods containing seeds, 
thus completing the life cycle. The use of the seeds to the 
plant is simply to provide for other plants of the same kind, 
and to insure a supply of food for the early life of each. 
Man, however, hasTearned to take advantage of this habit 







222 


THE SEED AND THE SEEDLING 



of plants, to secure food for himself and his animals. He has 
also found ways of enabling the plant under cultivation to 
store up more food than it could do in the natural state. 

199. Economic Uses of Seeds. — In thinking of the seeds 
used as food, we must limit the term to its botanical meaning. 
Many articles of food, such as the cereal grains, are commonly 
thought of as seeds. Their use as food has already been 
discussed. (See § 197.) The real seeds that are of greatest 

use to man as food are 
those of the pulse family, 
especially beans apd peas, 
which alone are the source 
of most of the protein 
that is obtained from 
plants. The meats of 
nuts are another source 
of protein food. Mature 
peas and beans contain 
more food matter than do 
“ green peas” and “string 
beans/’ the latter being 
valuable more for the 
bulk they furnish than 
for their food content. 

Besides their use as 
food, seeds can be used 
as medicine, castor oil 
and mustard being common remedies that are obtained 
from seeds. Castor oil is also used as a lubricant in air¬ 
planes on account of its not being affected by the cold 
of high altitudes. Two valuable products are obtained 
from cotton seeds: one the oil which is used in preparing 
foods in place of lard and butter, animal fats; the other, 
thread and cloth which are made from the fibers covering the 
outside of the seeds. The fibers are removed by a process 


Figure 210. — Bean Seedlings. 

All the food these plants have used came 
from the cotyledons, as the jar contained 
only sawdust. 




DORMANCY 


223 


called ginning; then the seeds are pressed to remove the oil. 
The refuse forms a valuable food for cattle, especially when 
mixed with other foods. The length of the fibers varies 
on different species of cotton, and the uses which are made 
of the fibers depend on their length. 

Linseed oil is obtained from the seeds of the flax. It is 
used in making paint and other substances. 

200. Dormancy. — Most seeds have a rest period, or period 
of dormancy as it is called. This is longer in wild plants than 
in cultivated ones. In most seeds the dormant period is 
only from the summer of one year to the spring of the next. 
In pigweed, however, the seeds of any one year may require 
several years for development, owing to differences in the 
thickness of the testa. Those grow first which have the 
thinnest testa. Years may pass, therefore, before all the 
seeds of a single crop have grown. This fact and the great 
number of seeds produced are the two main reasons why this 
weed is so persistent. Once it has seeded, it has the ground 
supplied with seeds that will grow some one year hence, 
some two, and so on up to thirty years. Other weeds which 
produce seeds that can lie dormant for at least thirty years 
are shepherd's purse, black mustard, chickweed, and curly 
dock. Variations in the thickness of the testa in seeds on 
the same plant is an adaptation which prevents the plant 
from drying out even if unfavorable conditions cause the 
death of all the seedlings of any one year. Closely related 
to the dormancy of a seed is its viability , or power to grow after 
long periods of rest. It has been proved by experiments 
that the seeds of weeds mentioned above are viable or able 
to grow after a dormancy of thirty years. Such facts as 
have been established by experiment lead us to discredit 
stories about the growing of seeds that have lain in Egyptian 
tombs hundreds of years. 

Practical use can be made of this knowledge by any one 
who cultivates crops. For instance, weeds that depend on 


224 


THE SEED AND THE SEEDLING 




Figure 211. — Diagram of Grain of 
Corn. 

A , hard outer covering ; B, protein ; 
C, scutellum ; D, plumule of embryo ; 
E, hypocotyl; F, root; G, conduct¬ 
ing vessels of scutellum; H, place 
of attachment; /, digestive cells of 
scutellum ; J, K, starch. 


seeds for their propagation 
should not be allowed to go 
to seed; and the greater their 
ability to grow after lying in 
the ground for a year or two, 
the greater pains should be 
taken not to allow the seeds 
to get into the soil. 

Wheat sprouts easily after 
a very short period of dor¬ 
mancy. This makes it neces¬ 
sary for the farmer to protect 
the wheat from moisture as 
soon as it is harvested, lest 
it begin to grow before it is 
threshed. Wheat that has 
sprouted is of little value for 
flour on account of changes 
which have taken place in the 
food matter partly digested 


for the support of the young wheat plant. 

201. Corn “ Seed.” — A grain or kernel 
of corn, commonly called a seed, is like a 
bean (1) in containing 
a young plant, the corn 
embryo; (2) in con¬ 
taining food for the 
use of the embryo 
when it first begins to 
grow; and (3) in hav¬ 
ing marks upon it. On 
one side of the kernel 
is a depression beneath 
which the embryo lies. Above the de¬ 
pression on each kernel is a slight prom- 


Figure 212. — Un¬ 
sprouted Grain of 
Corn. 


Figure 213. — Plu¬ 
mule Ready to 
Break Out. 

Root free and grow¬ 
ing downward. 












CORN “SEED” 


225 


inence, the scar which marks the place 
where one thread of the so-called silks 
was attached. This is more prominent 
in pop corn. At the base is a stalk by 
which the kernel is attached to the cob 
during its development (Figure 211). 

Corn differs from the bean in the position 
of its embryo, which is at one side of the 
food supply. The latter is called the 
endosperm (en'do-sperm: Greek, endo, 
within; sperma, a 
seed). Another differ¬ 
ence between the two 
is that the com has a 
single modified cotyle- Figure 214 - — Plu - 

. n i f7 mule Free, but 

don called the scutel- Bent by Accident . 

lum (sku-tel'lum: 

Latin, diminutive of scutum, a shield)? 
the use of which is to absorb and di¬ 
gest the food and carry it to the embryo 
(Figure 212). The cotyledon of the 
com never appears above ground. The 
corn embryo has its leaves rolled into a 
tight, pointed bud, an adaptation which 
enables it easily to pierce the earth above. 
The root is at the lower part of a short 
hypocotyl. 

As the corn has but one cotyledon, 
it belongs to the class of plants known 
as monocotyledons (mon-o-kot-y-le'- 
don : Greek, mono, one ; kotyledon, socket). 
The bean, having two cotyledons, be- 
™u™r ton© 3 t0 the class dicotyledons (di-kQt- 
Root system develop- y-lg'd6n: Greek, di, two; kotyledon, 
ing*. socket). 









226 


THE SEED AND THE SEEDLING 



LABORATORY STUDY OF CORN 

Draw a grain of corn, broad end up, 
with the side showing the depression 
towards you. Label (1) silk scar on one 
side of top; (2) scutellum (under de¬ 
pression); (3) stalk by which it was 
attached to the cob (hilum ?). 

Cut lengthwise a kernel that has been 
soaked for half a day. Label (1) em¬ 
bryo, young plant; (2) scutellum (cotyle¬ 
don) lying under embryo; (3) endosperm, 
store of food on which scutellum rests; 
(4) hard outer covering. Cut a kernel 
crosswise. Draw it, and label the parts 
as above. 

Remove the embryo.* Draw. Label 
plumule and root. Remove the scutel¬ 
lum. Draw. 

Remove the scutellum from each of 
several grains of corn when softened by 
soaking. Remove some of the white 
part of the grain. Apply the test for 
starch and decide whether the white 
part of a corn grain contains much starch. 
Now place a thin layer of moist corn 
starch in a watch glass and upon it lay 
several scutella. Cover with a bell jar 
and set in a warm place overnight. 
Then test with Fehling’s solution. What 
change has taken place? What is the 
name of the process which changes starch 
to sugar ? Invent an experiment to 
show the same change without removing 
the scutellum from the grain. (Hint, 
use wheat or oats.) 

Examine seedlings you can find in 
garden or field and classify them as mono¬ 
cotyledons or dicotyledons. 


Figure 216. — Advanced Corn 
Seedling. 


202. Classification of the Com¬ 
mon Seeds. — The comparative 








CLASSIFICATION OF THE COMMON SEEDS 227 


study of the bean and corn seeds shows the important parts 
of seeds and explains the chief differences between them. 
Some common seeds are classified as follows: monocotyle¬ 
dons, e.g. corn, grass, wheat, barley, rye, oats; dicotyledons, 
e.g. bean, squash, morning glory, tomato, radish, and beet. 

LABORATORY STUDY OF BEAN 

Draw a bean in an upright position, holding the side towards you that 
has the hilnm (a mark) on it. Label hilum. Near one end of the hilum is 
a small dot, the micropyle. Around the outside of bean, lengthwise, 
is a band or ridge, the raphe, ending at the hilum. Label micropyle and 
raphe. Split a soaked bean along the back. Draw the two parts. 
Label them cotyledons. On one of" them is the embryo or young plant. 
Draw and label: (1) the pair of small, white leaves, the plumule or seed 
bud of the new plant; (2) the hypocotyl, below the plumule, from which 
stem and roots will grow; (3) testa, the hard covering. 

Note. — Beans for class work should be soaked overnight at room 
temperature or for two hours in warm water. 

Beans should be first soaked for several hours, then planted about a 
week before the lesson on seedlings. 

Remove most of the cotyledons of a bean embryo. Place it in 
the earth or damp sawdust beside one which has whole cotyledons. 
Make sketches at each laboratory period to show the difference. What 
does this experiment show? Repeat the experiment with other seeds. 

SUGGESTIONS FOR HOME WORK 

Place a few beans in dry sand in a warm room. Why do not the 
beans grow and sprout? Place others in water in a warm room. 
What happens? Place other beans in moist earth (a) in a warm 
room; (b) in a cool place. Examine in a few days. These several 
experiments show the influence of temperatures, soil, and moisture on 
the sprouting of beans. Heat a few beans in an oven for 30 minutes 
and then place them in a warm, moist soil. Why do they not grow? 
Soak beans for 24 hours. Remove the testa and place them beside 
dry beans for a few days. What happens? This experiment illustrates 
one use of the testa. 

Remove most of the endosperm from a few kernels of corn. Plant 
these and compare the seedlings from time to time with those from 
whole kernels planted at the same time in the same dish. 


228 


THE SEED AND THE SEEDLING 


Place a box of soil in a warm room and keep it moist. Observe 
how many kinds of seedlings grow and how each gets out of the testa. 
How many kinds of seedlings do you find growing in your yard or 
garden ? 

203. Kinds of Foodstuffs Found in Seeds. — In the bean 
seed, two kinds of foodstuffs are stored, namely carbohydrates 
and proteins. Carbohydrate (see page 13) is the name 
of the foodstuff which includes the starches and the sugars. 
Protein (see page 14) is the name given to the food¬ 
stuff found in such foods as lean meat, cheese, and the white 
of egg. Beans contain more protein than any other seeds. 

Corn contains starch, sugar, and oil. Flaxseed and castor 
beans contain much oil. 

204. Foodstuffs in the Bean. — The presence of different 
kinds of foodstuffs may be shown by applying the following 
(chemical) tests. Boil beans until they are soft and then 
place a small portion of them in a test tube. Add water 
and heat. Put in a drop of iodine. If starch is present, the 
mixture will turn blue in color. Add strong nitric acid to a 
second portion in a clean test tube, boil and cool. If protein 
is present, the mixture will be a clear yellow color which will 
become orange if ammonia is added. To a third portion 
add Fehling’s solution 1 2 as a test for sugar. If the latter is 
present, the mixture will become dull orange when heated. 
Test uncooked seed for oil (1) by heating it over a lamp on a 
sheet of linen paper; (2) by soaking it overnight in ether. 
(This must not be near a flame at any time.) If oil is 
present, it will show on the paper as a clear spot, and in the 
second test the oil will appear on the surface of the ether in 
the test tube. 


1. Copper sulphate. 9 gra ms 

Water. 500 cc. 

2 . Rochelle salts. 49 grams 

Caustic potash.30 grams 

Water . •. 250 cc. 


Take two volumes of 1 , and one of 2, and add to the mixture 2 volumes 
of water. Do not mix 1 and 2 until ready to use. 








RESPIRATION 


229 


205. Where Foodstuffs Are Stored in Seeds. — In the bean, 
we have seen that both carbohydrates and proteins were 
stored in the cotyledons, evenly distributed, so far as we can 
discover. In the endosperm of a corn grain, the carbohy¬ 
drates are under the scutellum, and the proteins in a 
distinct layer outside of the carbohydrates, covered by the 
flinty outside coat of the grain (see Figure 211). 

206. Digestion of the Food in the Seed. — It may appear 
strange that the growing bean plant lives upon the food stored 
in the cotyledons and yet such is the case. But this food must 
undergo a real digestion before the bean embryo can use it. 
We do not know just how this digestion takes place in the 
bean, but in the corn, as we have learned, there is a special 
structure, the scutellum, which helps to digest the food in the 
endosperm. This corn scutellum may be removed from the 
corn seed and made to digest other kinds of starch, for in¬ 
stance, that obtained from a finely grated potato. To 
show the action of the scutellum on potato, this should be 
kept warm and moist for several hours, after which the di¬ 
gested starch may be tested for sugar with Fehling’s solution. 
When scientists learn more about the digestive processes of 
plants they will probably find that they are similar to the 
same processes in animals. 

207. Respiration. — Germinate a handful of soaked peas 
or other large seeds in a bottle with a wide mouth. Fit the 
bottle with a rubber stopper with one hole in it. Bend 
into U shape a glass tube of suitable size to fit the hole, but 
with one arm longer than the other. Insert the short arm 
just through the stopper, and let the longer one dip into a 
beaker containing lime water. Set aside overnight. What 
is the appearance of the lime water? What gas causes this 
appearance ? Where does it come from ? Why are seeds used 
in this experiment ? (Answer after studying photosynthesis.) 

Boil a few ounces of water to drive out all the air. Cool 
it. Place some seeds in it and pour linseed oil over the top 


230 


THE SEED AND THE SEEDLING 


of the water to shut out air. Set aside and examine from 
time to time. Do the seeds sprout? Why? 

Describe all the experiments above, making sketches of all 
the apparatus used. 

Plant a seedling in damp sawdust with its plumule up and 
its roots down. Plant another beside it in any other position. 
After a day or two examine them all. What direction does 
the root always tend to take? the plumule? 

Place a seedling in a jar before a window. What direction 
does it take? Turn it around. What happens after a 
few hours? Try the same experiment with an older plant. 
Which turns more quickly? Describe these experiments 
and invent others to show the same thing. 

SUMMARY 

The seed contains a new plant and food for its early life. 
The hypocotyl is the part of the plant (embryo) that helps 
it to get out of the ground. Growth of a seed depends on 
air, warmth, moisture, and on the food stored up in the 
cotyledons. Man uses the seeds for food because they con¬ 
tain starch, sugar, protein, and fats. 

QUESTIONS 

Name the parts of a seed. Name the adaptations of a seed. What 
is dormancy? viability? How can you show what conditions are 
necessary for germination of a seed? 

REFERENCES 

Ovule to Seed. 

Bessey, College Botany, pages 286-288. 

Snyder, General Science, page 105. 

Bergen and Caldwell, Practical Botany, pages 21-23. 

Seeds and Seedlings. 

Snyder, General Science, pages 202-206. 

Bergen, Foundations of Botany, pages 5-13; 14-24; 25. 

Bergen and Caldwell, Practical Botany, pages 136-145. 

Gibson, Sharp Eyes, pages 23-29. 


SEED SELECTION 


231 


PRACTICAL APPLICATIONS 

208. Seed Selection. — Farmers who try to secure full 
returns for the labor expended make it a point to select 
seed carefully. In several states granges and other organi¬ 
zations offer courses of instruction *as to what constitutes 
good seed and form clubs among the boys and girls who 
compete for prizes for yields of superior quantity and quality 
from selected seed. 

Testing of Seed. — The appearance of seed alone, how¬ 
ever, is not a sufficient basis for the production of a full 
crop, so it must be tested for its viability. There are many 
methods of making these tests, depending on the size of the 
seeds and the number to be tested. Anyone can perform 
the tests for himself who can provide suitable growing 
conditions for the seeds (see page 227). It is essential to 
success that accurate records be kept of the results of the 
experiments and tests. 

Preparation of Soil. — Having learned from tests that 
he has seed which has a high percentage of viability, the 
farmer’s next problem is how to prepare the soil for it. The 
preparation consists in making it fine and soft by plowing 
and harrowing, and in mixing the fertilizer thoroughly with 
it. The depth to which soil is plowed and the degree of 
fineness to which it is reduced are determined by the kind of 
crop to be planted and the amount of cultivation it can 
receive while it is growing. In any case, it must allow the 
roots to penetrate it easily, for it is from the soil that the 
roots gather moisture and food material for the plant. 

In addition to knowing that his seed will grow and that the 
soil is in proper condition for it, the farmer must know when 
to plant his crops. Some will not be injured by light frosts, 
while others must not be planted till all danger of frosts 
is past. He must know too, how deep to plant his seeds, 
and how firmly to press the soil over them in order to have 


232 


THE SEED AND THE SEEDLING 


them germinate normally, as well as how many to plant in a 
given area. 

When his crops are above ground, many of them, corn for 
example, must be cultivated. In cultivating, three objects 
are kept in view, (1) to keep the soil loose enough for the 
roots to penetrate it easily, (2) to conserve moisture, (3) 
to kill weeds. 

Thinning and Transplanting. — Crops like garden vege¬ 
tables will not grow to full size unless each one has sufficient 
room. On the other hand, a greater yield can be secured 
by transplanting to fill all vacant spaces. Transplanting 
tomatoes, peppers, and other plants grown in greenhouses 
makes it possible to secure ripe fruit earlier than if they were 
first planted out of doors after danger of frost. 


CHAPTER XVII 


THE FRUIT 

209. Definition. —The fruit of a plant is the final result 
of the work of the flower. In its simplest form it is the 
ripened ovary and its contents including the seed or seeds. 
In some ‘cases, however, it involves accessory parts of the 
flower as well, especially the receptacle. The wall of the 
ovary in a fruit is called 
the pericarp. Peculiarities of 
the pericarp will be men¬ 
tioned in connection with 
different kinds of fruit. 

The fruit is of use to a 
plant in two ways, (1) in pro¬ 
tecting the seeds during their 
development, as in the bean, 
or during their period of 
dormancy as in the nut, and 
(2) in helping to distribute 
the seeds after they are matured, as in the dandelion. 

The fruit of most plants is the part that is of greatest use 
to man, furnishing him most of the necessaries in the way 
of food, and many of the luxuries. 

LABORATORY STUDY 

Study of an Orange. — Examine the stem end and note the remains 
of the calyx. How many sepals had the flower ? Remove it. How 
many dots do you see ? These represent the ends of the vascular bun¬ 
dles which supplied food to the growing fruit. Examine the opposite 

233 



Remains of Pistils 
Remains of Stamens 


Fleshy Wall 
of Receptacle 


Developing 

Seeds 


Figure 217. — Diagram of Fruit 



234 


THE FRUIT 


end for scar showing where the pistil was attached. Scrape the skin or 
pinch it, and note the oil which shows as a yellow, odorous liquid. 

Note. Place a drop of this oil on linen paper. Note the spot it 
leaves. After a day examine the paper. Is the spot still visible? Oils 
that evaporate, leaving no spot, are called volatile or essential oils. 
Place peanut, Brazil nut, or castor bean on a linen paper. Heat till a 
clear spot shows. Lay aside and examine from time to time. Does 
the spot disappear? Oils that do not evaporate are known as true oils. 



Figure 218. — Cross Section of Orange, a Berry. 

A berry in the botanical sense is a fruit in which both exocarp and endo- 
carp are fleshy or juicy, although the seeds themselves, imbedded in the 
flesh, may be hard or even stony. Oranges, cranberries, huckleberries, 
currants, grapes, and tomatoes are true berries. A, rind; B, seeds; C, pulp. 

Make a cross section through the middle of the orange. How many 
distinct parts are there ? Where are the seeds ? Note the oil glands in 
the cut skin. Draw and label the parts named above. 

Remove the skin from a whole orange and separate the parts. How 
many are there ? Look for a strand of connective tissue on each one. 
Where do they come from ? Compare the number of sections with the 
number of vascular bundles on the stem end. 

210. Study of a Tomato. — Examine the whole fruit for 
traces of parts of the flower. On which end are they found ? 
How many sepals were there in the flower? Remove the 
stem and count the number of vascular bundles. Make a 
cross section through the middle. How many divisions in 





STUDY OF A TOMATO 


235 


the tomato? Where are the seeds? Note the mucilage with 
which each is surrounded. Can you see the vascular bundle 
which entered it? Note 
the very thin skin. Draw 
and label all. 

Note. Tomatoes can be 
obtained at any time of the 
year. Canned, unpeeled to¬ 
matoes will serve the purpose. 

Small ones are as satisfactory 
as large ones. 

211. Study of an Apple. 

— Examine the whole 
apple. On the blossom 
end find the old sepals. 

How many ? In the end 
of the stem look for vas¬ 
cular bundles. Draw 
and label. Make a cross 
section through the mid¬ 
dle. Draw. Label the 
seeds in the papery pod (core). How many divisions has it? 
How many vascular bundles, as shown by dots near the core ? 

Make a vertical section. Label vascular bundles when 

seen, stem, fleshy wall of 
receptacle, and remains 
of sepals. Are the re¬ 
mains of sepals on the 
same end in the apple as 
in the orange ? 

Other Studies. — Re¬ 
view the study of the 
corn grain, and compare 
with grains of wheat. 

Figure 220. —Cross Section of Apple. Where is the SCUtellum 




Figure 219.— Vertical Section of Apple, 
a Pome. 


The pome, apple, quince, pear, etc., is 
a fleshy fruit in which the receptacle be¬ 
comes consolidated with the pericarp. The 
receptacle and exocarp become fleshy 
while the endocarp becomes papery and 
incloses the seeds, thus forming the core . 
The fruit of the rose, called a “hip,” 
shows the relation of parts. (Figure 217.) 






236 


THE FRUIT 


in the wheat ? Draw and 
label. 

Draw a pod of bean 
or pea showing valves, 
seeds, remains of sepals, 
and place where pistil 
was attached. Examine 
fruit of dandelion, milk¬ 
weed, and other weeds as 
you find them. 

HOME WORK 

Figure 221. — Chestnut, a Dry Fruit. See how many kinds of 
A, remains of staminate flowers; B, nuts; fruits you can find. Make a 
C, bur. list of fruits obtained. After 

studying orange in laboratory, 
study apple, tomato, and other fruits at home as suggested in the text. 



212. Classification of Fruits. — Fruits may be grouped 
under two heads, (1) fleshy and (2) dry fruits. Dry fruits 
are of two kinds, (1) those that open, dehiscent (de-his's’nt) 
(Latin, dehiscere, to open) fruits, and (2) those that do not. 
open, indehiscent (Latin, in, not; dehiscere , to open). In- 
dehiscent fruits have been formed by the thin wall (pericarp, 
the wall of the ovary, matured) adhering closely to the seed, 
much as if a pod con¬ 
taining a single seed grew 
so firmly to it that it 
could not open. 

A grain of corn or wheat 
is a typical indehiscent 
fruit. The pericarp, 
though very thin, is hard 
and flinty, furnishing Z22.-s»u*^ thesW.nged Fku.t 

effective protection to the A dry , Indehiscent frulti adapted t0 distri _ 
inclosed embryo and food. bution by the wind. 








CLASSIFICATION OF FRUITS 


237 


The following table shows the main kinds of each group : 


Dry : 

Dehiscent: 

Pod Follicle 

Loment Silique 

Capsule 

Indehiscent: 

Nut Grain 

Samara Akene 

Fleshy : 

Berry Pome 

Drupe Multiple 

Aggregate Accessory 



Dehiscent fruits show 
many adaptations, most 
of which are based on 
some peculiarity of the 
pod. Take the bean for 
example. The pod is 
elastic. When it dries 
this causes it to split, 
then to curl up, throw¬ 
ing the seeds out by force. 
Another adaptation is 
that the funicle (see § 193) 


Figure 223. — Leaf, Flowers, and Fruit 
of Witch-hazel. 

This picture was made in October when 
the shrub blossoms. It is pollinated by 
insects that fly in the late fall. The fruit 
remains dormant during the winter and 
starts to develop in the spring. By fall it 
is mature and the exploding fruit scatters 
the seed. The name witch-hazel is said 
to have been given because it seems to fruit 
first in the spring and then blossom in the 
fall. It was supposed to be possessed by 
witches ; hence the name. The name was 
given way back in the time when ignorant 
people explained things they didn’t under¬ 
stand by ascribing them to the witches. 


dries up and falls off when 
its work is done, leaving the seeds free in the pod. A pod 
which has elastic tissue is the wild cucumber which forces 


its seeds out violently. Still another is the witch-hazel. 
A pod which explodes violently is that of the jewel-weed 
which requires only a touch to set it off, scattering the seeds 
far and near. 


A capsule differs from a pod chiefly in having more than 
one chamber in immature stages. A capsule usually splits 



238 


THE FRUIT 



^Chinks 


in several places, one for each chamber of the 
ovary, an adaptation for releasing all the 
seeds. Thus the violet spreads its valves 
wide open and does it suddenly, by this 
means throwing its smooth, 
hard seeds to a distance of 
several feet. The capsule 
of the poppy opens at the 
top by a number of chinks 
which appear just under 
the projecting lid. The 
capsule remains upright on 
a stiff stalk, which tips this 
way and that when the 
wind blows, scattering the 
small seeds. The plantain 
has a capsule which opens with a lid exposing 
a mass of seeds which are easily blown about 
by the wind. The special adaptations of the plantain are 
that its stalk remains upright after snow falls and that the 


Figure 224.—Cross 
Section of Cu¬ 
cumber, a Pepo. 
(A Fleshy Fruit.) 

Note the three 
seed chambers. 


Figure 226. — 
Capsule of 
Poppy. 

This contains 
several cham¬ 
bers and numer¬ 
ous small seeds 
which are shed 
through the 
chinks when the 
wind tips the 
stiff stalk. 



Figure 225. — Capsule of Violet. 

A dry, dehiscent fruit formed from a 
compound carpel. Note the three cham¬ 
bers and the numerous seeds. The dry¬ 
ing of the capsule causes the seeds to be 
pinched off and sent a foot or two away. 


lid does not fall off until 
the ground is covered with 
snow. The light seeds in 
great numbers are blown 
on the snow and carried 
long distances when it is 
smooth. These adapta¬ 
tions cause plantain to 
become a troublesome 
weed. Purslane, another 
weed, opens its capsule in 
the same way. Sodoespor- 
tulaca, a cultivated plant. 
This form of capsule is 
called a pyxis or pyxidium. 











CLASSIFICATION OF FRUITS 


239 



Figure 227.— Dry 
Fruits. 

1. Beechnut. The seed 
is inclosed in the pericarp 
(.4), and the whole sur¬ 
rounded by the bur ( B), 
which was formed from 
the involucre. 

2. Acorn. C , cup formed 
from involucre; D , seed 
inclosed in pericarp. 



The adaptations of fleshy fruits are 
(1) a sour or bitter taste during de¬ 
velopment. This 
prevents their 
being eaten before 
the seeds are ma¬ 
ture. (2) Edibility 
when ripe. This 
insures their being 
eaten by some ani- 
mal, sometimes 
without the seeds, 
which are likely to 
be dropped some 
distance from the 
plant which pro¬ 
duced them; or 
seeds and all, in 
which case the un¬ 
digested seeds are 

passed off with other wastes, often 
very far from the parent plant. Cedar 
trees, wild fruit trees, blackberry bushes, and asparagus grow¬ 
ing by fences or in the crotches of trees show the effectiveness 

of this form of adaptation. 

In fleshy fruits, most of 
the modifications are associ¬ 
ated with the pericarp which 
develops in zones or layers. 
The group of fleshy fruits 
known as “ stone fruits ” or 
drupes has a thick fleshy 
outer portion (exocarp) 
which incloses the inner 
stony part (endocarp). 


Figure 229. — Akene 
of Dandelion. 

A , pappus ; B, fruit. 



Figure 228. — Vertical Section of 
Peach, a Drupe. 

Note the stone in the center in 
which the seed is inclosed. The 
white fibers are vascular bundles. 








240 


THE FRUIT 



Blackberries and raspberries are collections of small drupes 
which make up an aggregate or collective fruit. In the case of 
raspberries, the fruit separates from the receptacle which re¬ 
mains on the stem. In blackberries it does not separate, but 
the receptacle is removed from the stem as part of the fruit. 

Accessory fruits are fleshy fruits in which the pericarp 
may be seated upon the receptacle or it may be inclosed by 

it. The strawberry has 
a fleshy receptacle in 
which the true fruits, 
akenes, lie in depressions. 

Multiple fruits are 
those in which two or 
more separate flowers 
may blend into a single 
mass, as in the mul¬ 
berry and the pineapple. 
Pineapples, through long 
cultivation, have lost the 
habit of producing seeds. 

213. Seed Dispersal. 
— Before any fruit has 
fulfilled its function, it 
must scatter the seeds it 
contains. This is neces¬ 
sary for three reasons, at 
least. (1) There would 
be too much competition 
if all were dropped near 
together; (2) there would 
be too slow progress, for 
the soil near the parent 
might be depleted, and the new plants could not grow as well 
there as in fresher soil; and (3) there would be too great a 
chance of extermination if all were dropped near together, for 


Figure 230. — Seed Dispersal of Milk¬ 
weed. 

The pod opens, exposing the seeds. The 
air causes the long, silky hairs attached 
to each seed to dry and spread, helping to 
force the seeds from the pod, and enabling 
the wind to carry them long distances. 





SEED DISPERSAL 


241 


some one unfavorable condition might kill them all. In order 
to scatter seeds a plant makes use of wind, animals, and water 
as distributing agents, and of such mechanical devices as 
exploding pods. To be distributed by the wind, a seed or a 
fruit must be light. This is brought about in some plants 
by plumes as in the case of the akene of the dandelion, 
thistle, and clematis, by the down on a milkweed seed, and 
by the wings on the fruits of the maple and elm. (Review 
§ 209.) To be carried by 
animals, the adaptations 
may be of two kinds — 
either they must have 
hooks to catch on or they 
must be edible. The bur¬ 
dock and beggar’s tick 
represent the first kind 
of adaptation, and the 
fleshy fruits the second. 

In some cases only the 
fruit is eaten, as with 
peach, plum, etc., and 
the seeds dropped; and 
in other cases the seeds 
and all are eaten, but are 
not acted upon in the 
digestive tract, and so 
are dropped far from the spot where they grew, as with 
berries, apples, pears, etc. (Review § 212.) 

To be carried by water, the adaptations must be such 
as will insure buoyancy and the ability to withstand decay. 
Both are well illustrated by the coconut, and the former 
by the cocklebur. To be distributed by being forcibly 
expelled, the fruits must have elastic tissue. The jewel- 
weed or touch-me-not illustrates this, as does witch-hazel, 
wild cucumber ; and violet (see Figure 225). 



Figure 231. — Fruits Distributed by 
Animals. 

A, avens ; B, hound’s tongue ; C, cockle- 
bur; D, burdock. 






242 


THE FRUIT 


Special devices for wind distribution are found in the 
Russian thistle and in tickle-grass, a common garden weed. 
In the former case the whole plant breaks off at the level 
of the ground, and is blown about by the wind, fruits and 
seeds being broken off and scattered as it rolls along the 
ground. This is one of the worst weeds of sections of the 
western states. In tickle-grass, only the panicle is broken 
off, but the result is the same. 

Besides the distribution of seeds by means of scattering 
the fruit or the seeds, plants have other means of propagating 
themselves which will be spoken of as they occur. The main 
dependence for keeping up the race, however, in most plants, 
especially the wild ones, is the distribution of its seeds. 
The fruit of a plant, so far as its relation to the plant that 
bore it is concerned, is simply a device for securing the dis¬ 
tribution of the seeds it contains. 

PRACTICAL APPLICATIONS 

214. Fruit. — The fruit-grower’s success depends largely 
upon his knowledge of the proper time for spraying his trees 
in the spring. (Review § 28.) He must wait till the bees 
have finished their visits, for he needs the help they give in 
pollinating the flowers. He must use a poison spray soon 
enough to kill the codling moth and thus prevent her laying 
eggs in the flowers or in the young apples, for this insect de¬ 
stroys much fruit. The best time is when the petals are fall- 
ing, for pollination is then accomplished and there is no danger 
of killing the bees, yet the harmful codling moth is kept from 
injuring the fruit. (Review structure of honey-bee and life- 
history of codling moth.) 

To secure the largest possible crop of strawberries, the 
gardener must be sure he has varieties that produce both 
stamens and pistils or at least that he has a sufficient number 
of staminate plants to produce pollen for the plants which 
bear only pistils. 


PRACTICAL APPLICATIONS 


243 


He should know, too, that the so-called false blossoms of 
the cucumber bear the pollen, without which the cucumbers 
will not develop in the pistillate flowers. 

The farmer should know that corn of different varieties 
like sweet corn and popcorn should not be planted in 
adjoining fields lest undesirable cross-pollination occur. 
Ears resulting from such pollination are uneven in size and 
show grains which differ in color from most of the other 
kernels. These are hybrids. He has probably learned 
from experience, however, that closely planted rows of corn 
in a field produce fuller ears than stalks standing alone. 
This is due to more thorough pollination. 

Fruit packers have learned that very careful handling is 
necessary in picking, sorting, and shipping fruit in order 
that the skin may not be 
broken. Broken skin ad¬ 
mits bacteria (see page 
309) which soon cause de¬ 
cay. Cold storage checks 
the growth of bacteria if 
any are present. 

For many years Smyrna 
has been the source of the 
fig supply of the world. 

The fruit-growers of Cali¬ 
fornia, seeing no reason 
why figs should not grow in 
that state, imported trees from Smyrna. Although these trees 
produced many blossoms, none of them matured into fruit. 
It has been customary since the time of Aristotle to hang 
branches bearing the wild, inedible fig in the Smyrna fig tree 
when it was in blossom. This wild fig, known as the caprifig, 
harbors the parasitic fig-wasp (Figure 232). The caprifig 
produces three kinds of fruit, spring, summer, and fall. The 
fig-wasp lays its eggs in the flowers of the caprifig (Figure 




244 


THE FRUIT 


233) and as it crawls about, its body becomes covered with 
pollen which is carried from flower to flower. Only the 
summer and fall flowers of caprifig produce pollen, and only 
the fall caprifig matures pollen at the time when the Smyrna 
figs are in blossom. The fig-wasp, seeking suitable flowers 
in which to deposit eggs, enters the Smyrna fig and leaves 
pollen from the flowers of caprifigs on the stigmas, thus 
fertilizing the Smyrna fig flowers which can now develop. 

It took many years of experimentation to discover all 
these intricate relations existing between the wild and the 
cultivated fig, and their dependence 
upon a certain insect to carry pollen. 
This is an extreme illustration of the 
interrelation between two closely re¬ 
lated plants and a parasitic insect. 

All these peculiar relations, how¬ 
ever, had to be worked out by scien¬ 
tists before the fig industry could 
become a success in California. Now 
Smyrna fig trees, wild caprifigs, and 
the fig-wasp have all been introduced, 
with the result that California’s fig¬ 
raising industry is a success. 

215. The Uses of Fruits to Man. — In speaking of the uses 
of fruits to man, it must be remembered that all the grains 
are fruits and that many so-called vegetables are fruits, 
as the tomato, the squash, and the cucumber. 

The most valuable source of food in the world is found 
in the cereals: wheat, oats, rye, rice, barley, and others. 
Nearly half of the population of the globe depends on rice 
for its principal food. Rice is the only one of the cereals 
that is commonly eaten entire. The others are usually 
ground and made into bread. The importance of bread as 
an article of food is shown by the term, “ the staff of life,” 
which is often applied to it. In the famine-stricken regions 




USES OF THE TERMS FRUIT , SEEDS , ETC. 245 

during the late war, the hungry cried for bread more than 
for any other article of food. A diet consisting of bread 
and nuts furnishes all the elements of food. 

Modern methods of grinding the cereals detract from their 
healthfulness as food because, in the refining process, all the 
coarser parts are removed, some of which contain substances, 
vitamines, essential to stimulating digestion. 

Not only are the cereals the most important article of 
food, but they are the basis of a great part of the world’s 
work. The raising of cereals, their preparation for food, and 
their distribution give employment to a greater number of 
persons than any other industry. Much more attention is 
now given to agricultural education than formerly, because 
its importance as an industry is better appreciated. Be¬ 
sides supplying man with food directly, many cereals are 
used to feed the animals which 'he raises for the meat, 
milk, butter, cheese, and eggs which they produce. Man’s 
beasts of burden live largely upon cereals too. 

The articles of food commonly known as fruits, — apples, 
oranges, berries, bananas, and others, — are valuable, their 
chief use being to supply variety to the diet. The fruits 
obtained from the vegetable garden,—tomatoes, cucumbers, 
squashes, egg-plant, melons, and others, — furnish some 
foodstuffs. Their main value, however, is to supply the 
bulk so necessary to the proper working of the organs of 
digestion. Incidentally, they add variety, and serve to 
make other food more appetizing. 

216. Uses of the Terms Fruit, Seeds, etc. —It will l?e evi¬ 
dent by this time, that the words fruit, seeds, and nuts have 
a different meaning in botany from their ordinary use. The 
term “ seed corn ” and “ seed wheat ” used by farmers is 
correct in the sense that it indicates the corn or the wheat 
which is planted or sowed to produce a new crop. The so- 
called Brazil nut of commerce is in reality a seed. The fig 
is a “ fruit ” composed of a thickened and hollow receptacle, 


246 


THE FRUIT 


the end of a branch, on the inside of which are produced the 
real fruits commonly known as seeds. 

HOME WORK 

What articles of food on your breakfast table were fruits ? Where 
were they raised? How were they brought to your home? What 
kinds of food were furnished by each? Look up the population of 
China, India, and Japan for the year 1915 or later. Most of these 
people live chiefly on rice. How does that compare with the number 
in the northern countries of Europe and the United States who live 
largely on the other cereals ? 

SUMMARY 

Reproduction is the ultimate object of the plant’s life, 
because it is the vital process which produces the seeds by 
which the plant is enabled to insure a new generation. 

The fruit serves to protect the seeds while they are growing, 
and to secure their distribution when they are ripe. The 
fruit of many plants is the part most useful to man, furnishing 
him the necessaries in the way of food, and many of the 
luxuries. Man has been able in some cases to improve the 
quantity and the quality of fruits for his own use. 

QUESTIONS 

What is a fruit? What is its function? Name the different kinds 
of fruits and give an example of each. 

REFERENCES 

Bessey, College Botany, pages 288-291. 

Bergen, Foundations of Botany, pages 217-227. 

Coulter, Plant Life and Plant Uses, pages 62; 325-335, 353-356. 

Abbott, General Biology, page 278. 

Bessey, College Botany, pages 324-326. 

Snyder, General Science, page 205. 

Bergen and Caldwell, Practical Botany, pages 146-148; 151-155. 

Gibson, Sharp Eyes, pages 4, 5; 150-155; 170-174; 205, 206. 


CHAPTER XVIII 


THE ROOT 

The root is the part of the plant which grows from the 
bottom of the stem. The roots of most plants are under¬ 
ground. Roots are the part of the plant that (1) gather 
water and food material from the soil; (2) that hold the 
plant firmly in the soil, 
and (3) in plants that 
live over the winter, store 
food to be used the fol¬ 
lowing year. 

217. Structure of a 
Root. — The outer part 
of the root is covered 
with a layer of epidermis 
called dermatogen (der- 
mat'o-jen: Greek, derm, 
skin). Inside of this is a 
region called the cortex 
or periblem (per'i-blem: 

Greek, peri, around) 
which surrounds the in¬ 
nermost region called the 
central cylinder or ple- 
rome (pler'om: Greek, plere, full). Near the tip, below 
the central cylinder, is a rapidly growing tissue, the meristem 
(mer'i-stem: Greek, meristos, divided), from which all the 
other parts develop. Over the end of the smaller roots is 
the root cap or calyptrogen (kal-ip'tro-jen: Greek, kalyptros, 

247 



Figure 234. — Cross Section of Root 
with Root Hairs. 

Note the relation of the hairs to the 
epidermal cells. Note also the irregu¬ 
larity caused by growth among the parti¬ 
cles of soil, some of which still adhere. 




248 


THE ROOT 


hidden). Each of these parts of 
a root adapts it to do its work. 
The epidermis keeps it from dry¬ 
ing. The region of the cortex 
contains the conducting vessels 
which carry water to the stem 
and digested food back. The 
central cylinder is the region 
where most of the food is stored. 
The root cap protects the tender 
end of the root from injury as it 
pushes through the soil, and the 
meristem tissue provides for re¬ 
newing all the regions of the root, 
and increasing their size. Besides 
the main root, there are many 
smaller roots which divide still 

Figure 235-Cross and Long.- further into rootlets. The root 
tudinal Section of Root. and its divisions underground 
may be compared, in a general 
way, to the stem, branches, and twigs aboveground. 

218. Root Hairs. — Root hairs are found a short distance 
back from the tip of each rootlet. 

Each hair consists of a projection 
of an epidermal cell. Root hairs 
are very numerous. As the root 
grows, the hairs farthest from the 
tip die and are replaced by new 
ones nearer the tip. Root hairs 
greatly increase the absorbing 
surface of a rootlet. They attach 
themselves firmly to particles of 

soil from which they are able to 
, , , . „ Figure 236. — Longitudinal 

take almost every trace of mois- Section through Root and 

ture by the process of osmosis (see Root Cap. 



















ROOT HAIRS 


249 


page 15). They alsc 
serve to fix the plant 
firmly in the soil. 

LABORATORY 
STUDY OF 
ROOTS 

Cut a root of carrot or 
parsnip lengthwise and 
identify (1) dermatogen, 
the epidermal covering; 

(2) cortex, the region 
under the dermatogen; 

(3) plerome, or central 
cylinder. Cut it cross¬ 
wise and identify the same 
regions. Make drawings 
of both sections and label 
fully. In both sections 
look for rootlets and note 
the region from which 
they arise. Show this in 
your drawing. 

Stand cut-off roots of 
parsnip overnight in water tinted with red ink. In what region does 
the color show? Make cross sections of one and longitudinal sections 
of the other. Draw both and describe. 

Look at the roots of seedlings furnished you. How does the extent 
of roots compare with the parts aboveground? 

Examine roots grown in a moist chamber for root hairs. Compare 
with one grown in sawdust or soil after it has been carefully washed. 

How do they differ? On 
what part of the rootlet are 
the root hairs most numer¬ 
ous? Where are they the 
longest ? 

Mark a root with a fine pen 
dipped in India ink, making 
the marks even and close to¬ 
gether (about 1 mm.). Ex¬ 
amine from time to time to 



Figure 238. — Bit of Epidermis of Root 
with Root Hairs. 



Figure 237. — Germinating Wheat, Showing 
Root Hairs. 


Notice the plumule growing up and the roots 
down. This grain of wheat was germinated in 
moist air, and not in the soil. Root hairs are 
seldom seen in soil grown seedlings, as they 
are so fragile that they break off and remain in 
the soil when the seedling is removed. 








250 


THE ROOT 


determine where growth is most rapid as shown by increased distances 
between marks. 

Test roots for the presence of starch, sugar, and protein, using the 
tests suggested for seeds. Make a report on what you find. 

In what direction do roots usually grow ? Try to make them grow 
in some other direction. Write what you did and show by drawings 
what success you had. 

Draw aerial roots of an ivy stem. 

Draw a cluster of fascicled roots of a dahlia or a buttercup or an 
anemonella. 

SUGGESTIONS FOR HOME WORK 

Pull weeds and examine the roots. Which have tap roots? Why 
do they flourish better than the plants around them? 

Cut a piece of thick sod with a sharp spade or trowel. How many 
grass plants in a square two inches on a side? What kinds of roots 
has grass? Wash the dirt away carefully and measure the extent of 
the root system. Compare it with the part aboveground. Do the 
same with other plants than grass. 

On how many nodes of a corn stem do prop roots grow ? What is the 
effect of “ hilling up” corn on the production of prop roots? 

Place willow twigs in water. Watch the growth of adventitious 
roots, noting especially the root caps. Do duckweed and other floating 
plants have root caps? Account for what you find. 


Examine a large number of roots and report. 



Roots All 
Under¬ 
ground 

Roots not 
All Under¬ 
ground 

Primary 

Roots 

Fibrous 

Roots 

i 

Aerial 

Roots 

Dandelion. 
Plantain . 
Carrot . . 

Dahlia . . 
Com. . . 
Ivy . . . 







FORMS OF ROOTS 

Tap or primary roots — adapted to penetrate the soil, 
deeply enabling them to secure water when plants with 
different roots cannot. Adapted also to the storage of food. 
















ROOT HAIRS 


251 




Figure 240. — Fascicled Roots of Dahlia. 
Used for the storage of food. 


Fibrous roots —a great 
many threadlike roots 
which extend in all direc¬ 
tions through the soil. 

Thickened fibrous roots 
— a modification of 
fibrous. 

Fascicled roots — a 
cluster of thickened roots 
for the storage of food. 

MODIFIED ROOTS 

Aerial roots for attach¬ 
ment. Ivy. Note how 
they grow from side of 
stem. 


Aerial roots for ab- Figure 239. — Fibrous Roots of the 
sorbing water. Certain Buttercup (slightly thickened). 

orchids, tropical plants which grow in the air. 

Water roots lacking root cap. Duckweed. 







252 


THE ROOT 



Knees — projections on roots of cypress. 

Adventitious roots — those that grow in unusual positions, 
especially from the end of a cut stem. Geranium, willow, 
any “ slip.” 

219. The Duration of Roots. — Roots which live only for 
a season are called annual roots, examples of which are corn, 

peas, beans, and other 
common garden plants. 
Those that store the food 
manufactured one season 
and use it to produce 
flowers and fruit the next 
are called biennial roots. 
The garden furnishes ex¬ 
amples of these in the 
fleshy roots of carrots, 
parsnips, beets, turnips, 
and vegetable oysters. 
Roots that live from year 
to year, like those of trees, 
the dandelion, burdock, 
horse-radish, peony, and 
“ pie plant ” are perennial 

Figure 241. — Aerial Roots of Ivy. 


These are used for attachment, growing 220 Extent of Root 
only on the side towards the surface on 

Which the stem lies. System. — The root sys¬ 

tem of a tree growing in 
fertile soil is about equal to the parts above the ground. 
An oat plant has a root system the combined length of which 
is about 154 feet; a wheat plant has single roots seven feet 
long; and alfalfa an enormous root system (see Figure 244). 
A single root of alfalfa may extend more than 20 feet in one 
direction in a loose soil. 

221. Specialized Roots. — The roots of the ivy which 
grow for attachment differ from ordinary roots not only in 





SPECIALIZED ROOTS 


253 


their function, but in 
their position. They can 
grow from any side of 
a stem, enabling them 
to attach themselves to 
a surface wherever they 
may happen to touch it. 

The haustoria by which 
parasite plants (see page 
369) get their food from 
the host are modified 
aerial roots. They are All tap roots are used for food storage, 
able to take food from and most of them are either biennial or 

the stem of the host by P erennial - 

absorbing pads, as is well illustrated by dodder. 

The cypress tree, which grows with its roots submerged, 
has peculiar projections which extend above the surface of 
the water. These so-called “ knees ” are so modified that 

the roots are enabled to 
secure the air they need. 

The pendant roots of the 
tropical orchids, known as 
velamens, have a modified 
outside layer which en-' 
ables them to absorb al¬ 
most immediately any 
water which falls on them 
and conduct it to the cen¬ 
tral cylinder for storage. 
This enables the plants 
possessing them to live 
outside of the soil (see 
page 373, epiphytes). 

Prop roots of corn grow 
from nodes above the soil, 



Figure 243. — Extent of Root System 


of Corn 90 Days After Planting. 
Note how the roots of adjoining hills 
mingle. This shows how keen the 
struggle is to get water and food, and 
how the soil is deprived of its food 
contents. 



Figure 242. —Tap Roots of Radish. 












254 


THE ROOT 



which they penetrate. This is an adaptation for holding 
the plant more securely than the ordinary roots could do. 
When mature, they branch freely. 

Adventitious roots are those which grow from unusual 
places, especially soil roots. It is the ability to form such 
roots that enables us to “ slip ” plants like geraniums, 
balsams, ivy, and Wandering Jew. Such garden plants as 


Figure 244. — Root System of Alfalfa. 

How far from the stem of the plant do you think the roots extended ? 

tomato, cucumber, squash, and others, put forth adventitious 
roots where their stems touch the soil, especially at the nodes 
in the case of the vines named. This is an adaptation which 
gives them a greater supply of food material near the leaves 
which use it, and which enables the plant to live even if 
broken from the main portion of the stem. 

Certain cactus plants which live in the desert have roots 
which are twenty times as long as the parts which appear 



ECONOMIC USES OF ROOTS 


255 



above the soil. This enables them to absorb and to store 
up the scanty moisture. 

222. Economic Uses of Roots. — In some plants the root is 
the most valuable part for food not only for man but also 
for his animals. Examples of this are many of the garden 


Figure 245. — Root System of Rhubarb, a Medicinal Plant. 

Food'is stored in the larger parts. Many of the rootlets have been broken off. 

vegetables, such as carrot, parsnip, turnip, vegetable oyster, 
and beet. The food stored in the beet is rich in sugar, 
making it one of the sources of the sugar of commerce as well 
as a valuable food for stock. Other roots furnish substances 
used as medicine when they have been extracted, as rhubarb 





256 


THE ROOT 


and mandrake, while the ground root of ginger is used in 
medicine and in cooking. The vegetable oyster is often 
found growing by roadsides where its seed has been blown 
from gardens. 

In the case of these roots, a few must always be saved to 
produce seeds for another crop, inasmuch as turnips, beets, 
carrots, parsnips, ^nd vegetable oysters are biennials, 
requiring to be planted the second season, when they use 
food stored during the first year to produce fruit and seeds. 

PRACTICAL APPLICATIONS 

Anything which concerns the condition of the soil in which 
plants are to grow and the amount of raw material available 
for food-making is important because of the relation of the 
roots to the soil and of their function to the plant. For this 
reason every one who raises plants should know the habits of 
each kind of plant he raises and try to make the conditions 
such as will best suit each kind of plant or crop. 

Soil that is well filled with roots is not subject to erosion 
as is barren soil. Use is made of this fact in planting certain 
grasses for their binding effect, especially on the coast where 
the constant washing of the waves has a tendency to change 
the coast line. 

The roots of leguminous plants become infested with 
certain bacteria found in the soil. These bacteria form 
bunches or nodules on the roots in which they live. Thus 
protected, they gather nitrogen from the air, use what they 
need, and store up the rest. This surplus is used by legumi¬ 
nous plants in making protein, part of which is found in the 
body of the plant, and part in the seeds. When the seeds 
are used as food, man and the animals secure the protein 
which they need. When the plants die, they leave the soil 
richer in nitrogen in a form that can be used by plants 
which do not have the help of the bacteria to gather it. 
So valuable is this form of fertilizer, that in some cases, 



PRACTICAL APPLICATIONS 257 

leguminous crops are raised and plowed under for the sake 
of the nitrogen in them, this being called “ green manuring,’* 
a practice which was carried on for a long time before the 
reason for its value was learned. 


Figure 246. — Effect of Inoculation on Garden Peas. 
No. 1, uninoculated. No. 2, inoculated. 






258 


THE ROOT 



The relation which exists between the plants which profit 
by the work of the nitrogen-gathering bacteria and at the 
same time furnish them protection is an illustration of 
symbiosis (sym-bl-o'sis: Greek, sym, together; bios, life), 


Figure 247. — Effect of Bacteria on the Growth of Red Clover in a 
Poor Sand. 

Left, uninoculated; right, inoculated. 

the relation of mutual helpfulness between organisms of 
different kinds. 

223. Inoculation. — Nitrogen-gathering bacteria are likely 
to be present in all soils in small numbers, but in order to 









INOCULATION 


259 


have them help plants to an appreciable degree, there must be 
many of them. It has been found possible to place them in 
the soil artificially, a process called inoculation. This is 
done either by wetting the seeds with water containing the 
bacteria, or by putting them into the soil in some other 
manner. Care should be taken to secure only pure cultures 
(see page 313) and to have them fresh. By the use of 
cultures a soil properly inoculated will not only produce 
larger crops of leguminous plants, but its quality is also 
improved for crops which follow them, as explained above. 

SUMMARY 

The root is the part of the plant that grows in the soil to 
gather water and food materials for it, to hold it securely, and 
to store food for it. Roots have many forms, the primary 
or tap root and the fibrous roots being the extremes. Small 
roots have a root cap to prevent injury to their tips, and 
root hairs to increase their absorbing surface. There are 
specialized roots for special purposes, such as aerial roots 
for support and for gathering water. Adventitious roots 
are those that grow on “ slips.” Roots form an important 
part of man’s food, and food for his animals. 

QUESTIONS 

What is the root? What does it do for the plant? Describe the 
structure of a tap root. How do fibrous roots differ from a tap root? 
In which kind of roots is most food stored? What use does the plant 
make of this stored food? What use does man make? What kinds 
of food are stored in roots? 

REFERENCES 

Bergen, Foundations of Botany, pages 62-129. 

Bergen and Caldwell, Practical Botany, pages 5-16, 24-38. 

Conn, Biology, page 112. 


CHAPTER XIX 


STEMS 

224. Definition. — The stem is that part of the plant 
which forms the connection between the roots and the leaves. 
It is adapted to its work (1) in being compact and sturdy, 
enabling it to bear weight; (2) in branching, to afford a 
larger number of points for the attachment of leaves; 
(3) (in some cases) in being provided with thorns or briers, 
as in the blackberry and rose, to protect it from being injured 
by animals; (4) in being covered with a strong epidermis 
or, in woody stems, with bark which protects it from outside 
injury and keeps it from drying up; (5) in plants which 
grow in the water, in having large air spaces to carry air 
to the roots which lie in the mud at the bottom of the water. 

An underground stem can always be distinguished from 
a root by the buds of new leaves or the scales of old ones, 
although in some the leaves are reduced to mere scales, as 
in the potato. Underground stems usually send up aerial 
shoots. They often have an advantage over an aerial stem 
in being better protected. Some plants make use of the 
underground stem in propagating themselves (see page 305). 

225. Position of Stems. — Stems assume a variety of posi¬ 
tions, but that which serves the purpose of most plants best 
is the upright, independent position. Any tree illustrates 
this kind of stem. A few which are upright keep that 
position by twining or by clinging to an upright support, 
which may be some other plant. These plants have com¬ 
paratively weak stems. Creeping or trailing stems lie on 
the ground with only the tip erect. This position is illus- 

260 


USES OF THE STEM TO MAN 


261 


trated by the habit of the ground pine and by the running 
blackberry. A creeping stem may lie beneath the surface 
of the ground, as in the case of the Canada thistle or the 
“ quack ” grass. (See also 
Figure 305, Pteris, and Figure 
311, Club Moss.) 

226. The Duration of 
Stems. — The length of life 
of a stem depends upon its 
habit in producing seeds. An 
annual or herbaceous stem, 
like the morning-glory or the 
lady-slipper, dies at the end 
of the first season, the plant having produced its seeds. 
Other stems, like the trees, last year after year. Some of 
the redwood trees in California are known to be more than 
three thousand years old, and the Cedar of Lebanon, grow¬ 
ing in Asia Minor, is known to live as long. 

227. Uses of the Stem to the Plant. — The stem is of use to 
the plant in being the place for the attachment of leaves, and 

in providing a path for the vessels which 
carry water from the roots where it is 
gathered to the leaves where most of it 
is used. A third use of stems is for the 
storage of food, as in the potato. A 
few plants make use of stems for propa¬ 
gation, as in the case of the strawberry 
and the raspberry (see page 271). 

228. Uses of the Stem to Man. — 
Man makes use of the stem for food, the 
potato being one of the most familiar 
examples as well as a common source of food. Starch is 
also made from potatoes. The stem and buds of asparagus 
are used for food. 

A second use is for shelter. Trees furnish lumber in all 



Figure 249. — Starch 
Grains Highly Mag¬ 
nified, Showing Lines 
of Growth. 



Figure 248. — Indian Turnip. 






262 


STEMS 


Bud 


its varieties. Some parts of houses can be' made from stone, 
brick, or other materials, but for the inside finishing we are 
still dependent upon wood. 

A third use is for furniture. No other material has been 
found that is so satisfactory as wood for tables and chairs. 

A fourth use is for clothing. The flax plant which furnishes 
the material from which linen is made is one of the most 
valuable. Its usefulness depends upon the bast fibers which 

it contains. These are found 
in the outer part of the slender 
stem and serve to give it stiff¬ 
ness. When separated from 
the other parts of the stem 
they can be twisted, spun, 
and woven. 

A fifth use is for cordage. 
This includes all kinds of 
ropes and many kinds of 
"strings. Some cordage’is ob¬ 
tained from fibers of hemp, 
and some from other plants. 

Among the many other 
uses of stems in our daily life 
may be mentioned poles for 
telegraph, telephone, and 
electric light wires, for the 
masts of ships, for the piles 
of piers, timbers for props of mines, lumber for bridge 
foundations, cross-ties of railroads, besides parts of imple¬ 
ments and tools of daily use, vehicles and parts of ma¬ 
chines by which many of these are made. Add to these 
the boxes, barrels, crates, trunks, pails, baskets, and other 
common articles which we use frequently, and paper in its 
many forms and numerous uses. It is evident from this 
list, which is far from complete, that man has found the 



Lenticels 


Attachment to 
AeFiai Stem 


Figure 250. — Potato, Sometimes 
Called a Tuber. 

A form of underground stem used for 
storing food. 




SPECIALIZED STEMS 


263 


stems of plants to be of great use to him, and that he could 
not well do without them. 

229. Adaptations of Wood. — When we compare the number 
of articles that are made of wood with the same articles made 
of substitutes, we see that there are some good reasons for the 
use of wood. Among these are its lightness compared with 
iron or steel for use in furniture, trunks, and other articles, 
its elasticity , its toughness, its durability, especially when pro¬ 
tected from dampness, the ease with which it can be shaped 
by tools, and its beauty, depending on color and grain, and 
on the high polish it can take. 

230. Specialized Stems. — In regions where the climate is 
very hot and dry most of the year, the leaf surface is greatly 
reduced to prevent undue 
evaporation. In this case 
the stem becomes green 
and performs the work of 
photosynthesis (see page 
278), ordinarily done by 
leaves. The cactus illus¬ 
trates this. Certain other 
plants have no leaves but 
the stem branches in such 
a way as to resemble 
leaves. The florist’s smilax and asparagus fern represent this 
kind of branching. The true leaves are reduced to minute 
scales. 

LABORATORY STUDY OF STEMS 

Draw a potato. Label the “eyes” buds. On which end are they 
more numerous? Label scale, just above bud. Note end where it 
was attached to the main plant. 

Cut off the stem end and stand in water colored with red ink. After 
two hours examine again and note what part is stained. Cut off slices 
till traces of color disappear. Draw to show where it is colored- Cut 
a thin slice and put a few drops of weak iodine on it. What happens? 
What does it show? 



Figure 251. — “ Stemless ” Plant — 
Dandelion. 





264 


STEMS 


Cut an onion vertically. Note the condensed stem on which the 
leaves are arranged. 

Draw a twig of horse-chestnut in winter condition. Label rings 
(scars of scales), terminal bud (on end), lateral buds (on sides), leaf scar 
(oval mark below bud), vascular bundles (on leaf scar). How many? 

How are the lateral buds ar¬ 
ranged? Remove the scales 
carefully. Count and draw 
them. Describe them. What 
do you find inside? Draw 
and describe. 

Compare with twigs of 
other trees — hickory, elm, 
maple, basswood. What dif¬ 
ferences do you notice? 

231. External Appear¬ 
ance of Woody Stems.— 

If we take for an example 
a twig of the horse-chest¬ 
nut, we shall find on the 
outside a brownish bark, 
some scars showing the 
position of last year’s 
leaves, and some rings 
extending around the 
twig, indicating where 
the scales were attached 
that covered the bud 
containing these leaves. 
Above this scar will be 
found a bud covered with 
sticky scales and at the 
end of the twig a large terminal bud. The buds which grow 
above the leaves are called axillary buds. If more than one of 
these is found in an axil the additional ones are called acces¬ 
sory buds. The strength of the terminal bud determines 

the kind of branching of a trunk. A single very strong 



Figure 252. — Stem of Horse-chestnut. 

A , a season’s growth ; B, termin’al bud ; 
C, lateral bud; D, leaf scars; E, fibro- 
vascular bundles; F, rings caused by 
scales of last year’s terminal bud. 







GROWTH OF STEMS 


265 


terminal bud gives the excurrent (Latin, ex, out; curro, 
to run) trunk of the evergreen trees, and a number of terminal 
buds of equal strength give the deliquescent (Latin, de, 
from; liquescere, to become liquid) branching of the elm 
and other trees. Between these extremes there are many 
intermediate forms. The buds for next season’s leaves are 
formed very soon after the leaves have reached their full 
size in the spring. Buds are protected in winter by coverings 
of scales which prevent them from becoming dry. A bud 
may contain leaves only, 
or flowers only, or both. 

Small markings on the 
smooth bark are lenticels, 
spots where the outer 
layer of the branch is 
broken, allowing air to 
enter the inner portions. 

232. Growth of Stems. 

— Most woody plants 
grow rapidly in the spring 
and early part of summer, Figure 253. — Elms. 

after which they cease in- Note the lack of a strong central stem 
creasing in size but con- and the repeated dividing of the branches, 
tinue to add material illustrating the deliquescent stem. 

which makes wood, thus enabling the stems to resist killing 
in the winter. Such plants are said to have a definite annual 
growth. This is illustrated by most woody trees. Other 
plants continue to grow until the end of the season. The 
latest formed wood in such plants is usually killed by the 
frost, with the buds on it. The plant begins to grow next 
season from axillary buds below the point where it was killed. 
Such plants are said to have indefinite annual growth. Ex¬ 
amples are red raspberry and sumac. Advantages of definite 
annual growth are twofold: (1) it enables a tree to grow 
very rapidly in the spring when conditions are most favorable 





266 


STEMS 


for growth, and (2) it does not result in the loss of any 
wood once formed. On the other hand, the plant which 
makes an indefinite annual growth can take advantage of 
favorable growing conditions whenever 
they occur, although it may lose some of 
its youngest wood if frost comes before it 
is hard enough to resist it. 

In the annual growth of woody stems, a 
new node is added to each branch, and a 
new. layer of wood over the wood of previ¬ 
ous years. This makes it possible to tell 
approximately how many years old a tree 
is, the growth of each year forming a ring 
more or less distinct according to condi¬ 
tions. When the conditions for growth 
are at their best, the cells formed are large. 
As conditions become less favorable, the 
cells become smaller and have thicker 
walls, marking distinctly the end of one 
season’s growth from the beginning of the 
next. The size of the cells varies greatly 
in different trees, producing the “grains” 
which are so characteristic of each kind 
of lumber. 

233. Vascular Bundles or Fibro-vascular 
Bundles. — Vascular bundles are a part of 
the conductive system of the plant. They 
are in stem, root, and leaves. In the 
leaves we call them veins. In celery they 
are the “ strings ” (see Figure 256). 

234. Structure of a Vascular Bundle.—Avascular bundle 
in a monocotyledonous plant is made up of two kinds of cells 
or groups of cells called xylern (zy'lem) and phloem (flo'em). 
The xylem cells are thick-walled, but with thin spots in each 
cell where it touches another cell of the same kind. Each 



Figure 254. — Wood 
of Spruce, Greatly 
Magnified. 

A, large cells 
formed early in sea¬ 
son ; B, E, small 
cells formed late in 
season; C, resin 
duct; D, medullary 
ray. 












ARRANGEMENT OF THE VASCULAR BUNDLES 267 

cell is long and pointed. Some of these cells overlap in such 
a way that they make continuous tubes from the root, up 
through the stem, and into the leaves. The thick walls help 
to give firmness to the plant. 

The phloem cells are the other part of the vascular bundle 
in a monocotyledonous stem. They have thinner walls than 
the xylem cells and they communicate with one another 
through the ends and not 
through the sides. The 
ends of these cells have 
perforated plates through 
which the liquid in the 
cells passes. These are 
called sieve plates. 

In a dicotyledonous 
stem, the vascular bun¬ 
dles are made up of three 
kinds of elements, the 
phloem, like that of the 
monocotyledonous stem, 
and the xylem, also like 
that already described. 

Between them is a layer 
of thin-walled, brick¬ 

shaped cells called cam¬ 
bium where growth is 
taking place rapidly. This is the cambium or meristem 
tissue. The side towards the phloem is constantly produc¬ 
ing phloem cells, and the other side xylem cells. Associated 
with the phloem cells are bast fibers, the function of which 
is to give strength and firmness to the stem. 

235. Arrangement of the Vascular Bundles. — This differs in 
the two kinds of stems already mentioned. In the corn stalk, 
a monocotyledonous stem, the vascular bundles are scattered 
throughout the central pith, and the bundles have no definite 



Figure 255. — Cross Section of Corn 
Stem. 

Note the fibro-vascular bundles scattered 
throughout the pith. 




268 


STEMS 


position with reference to the center. The outside of the 
stem is covered with a hard rind which often contains silica, 
a substance like glass which makes it hard and strong. In 
grasses, the stem is hollow, and the bundles are of course 



around the edges, some of them 
passing off at each node into the 
leaf which arises from it. 



Figure 257. — Part of Cross 
Section of Young Dicotyle¬ 
donous Stem. 


Figure 256. — Corn 
Stem, Broken. 

A, node; B, hard 
outer rind; C . pith; 
D, fibro-vascular bun¬ 
dles. 


Note the arrangement of the 
fibro-vascular bundles. These 
gradually form a complete ring. 
The cambium layer in an older 
stem lies under the bark. Its 
color is green. 


236. The Work of the Vascular Bundle. — We have said that 
the vascular bundles are a part of the conductive system of a 
plant, and that some of the cells form vessels. There is little 
likeness to the vascular system of animals, however, for the 
system in plants lacks an organ for driving the liquid in the 
tubes, and it has little use as an aid to respiration. Water, 



























THE WORK OF THE VASCULAR BUNDLE 269 


absorbed from the soil by the root hairs, is passed by osmosis 
to the slender cells in the roots, and from there up through the. 
stem and to the leaves, where it is used in photosynthesis. 
After the food made by photosynthesis^ is digested and 
thereby made ready for the use of the plant, some of it is 
carried down through the phloem part of the vascular bundle 
to such parts of the plant as need it. There is in this a like¬ 
ness to the circulation of animals in which fresh blood is 
carried in one set of vessels and blood that needs renewing 
in another set. The liquid which is carried in the vessels 
of plants is commonly called sap, and when a plant is broken, 
and the sap exudes, we speak of it as bleeding. 

HOME WORK —STEMS 

1. Examine the house you live in to learn, if possible, the kinds 
of lumber used for the floors, for the casings, and for the doors. What 
kinds do you like best ? Why ? 

2. Examine all the wooden furniture and answer the same 
questions. 

3. Examine the different kinds of matting. Of what is each 
made? Examine linoleum. Of what is it made? 

4. Examine the wicker furniture. Of what is it made? What 
is rattan? Bamboo? 

5. Examine your “straw” hat. Of what is it made? How? 

6. Examine the doormat. Was it made from any part of the 
stem of a plant? 

7. Examine the clothes-basket and the market-basket, and the 
sewing-basket, and try to decide from what each was made. 

8. Examine a trunk, a box, a barrel, a pail, a picture-frame, a 
harness, a wagon, an automobile, a fence, telegraph poles, paving 
blocks, corks, and toys of various kinds, to find what parts of them 
are made from wood, and what kinds of wood are used. 

9. Make a list of all the other things, as spools, that are made of 
wood. 

10. What substitutes for wood do you find? In what respects 
are they better? in what respects inferior to wood? 

11. How is paper made? 

12. What is celluloid? 

13. Where is thatch used? 


270 


STEMS 


14. What is oakum? In what industry is it used? 

15. Why is excelsior a good material for packing fragile articles? 

16. Into which of your garments does linen enter? 

17. What is jute? manila? burlap? 

18. How many trees do you know? Which do you like best? 
Why? 

PRACTICAL APPLICATIONS —STEMS AS A MEANS OF 
PROPAGATING PLANTS 

“ Slipping ” plants is a common practice, the success of 
which is due to the fact that adventitious roots grow readily 

from the cut end of a 
branch of geranium, bal¬ 
sam, ivy, and other 
plants. Two advantages 
make slipping popular: 
(1) the certainty of secur¬ 
ing a new plant like the 
parent plant, (2) the short 
time required to produce 
blooms compared with 
the same kind of plant 
raised from the seed. 
Willow twigs root so 
readily that it is often 
possible to start a hedge 
by sticking pieces of 
branches into the ground 
when it is very wet. 

Grafting is a common 
method of propagating 
trees. It depends for 
success upon putting the 
cambium layer of a twig from one plant against the cam¬ 
bium of another and fastening it there until the two layers 
have grown together, protecting it from moisture, insects, and 



Figure 258. — Cleft Grafting. 

In 1, the twigs or scions have been cut 
obliquely to expose the cambium. In 2, 
a branch of the stock has been split to re¬ 
ceive the scions. In 3, the scions have 
been inserted into the stock, cambium 
against cambium. (The outer part of the 
branch is represented as having been re¬ 
moved.) In 4, the wax has been applied. 






















GROWTH OF STEMS 


271 


fungi by a layer of wax. Usually a twig from a mature tree 
(the scion) is grafted upon the young stem of a seedling or on 
an inferior tree (the stock), producing fruit several years 
earlier than the seedling tree would. One can be sure, too, of 
obtaining the fruit wanted. If twigs from several kinds of 
trees be grafted upon a “ scrub ” tree, each twig will bear its 
own kind of fruit. At the same time the quality of the 
fruit on the tree’s own 
branches will be greatly 
improved. The pome 
fruits, drupe fruits, and 
citrus fruits are usually 
grafted. Greenhouse 
roses, azaleas, and other 
plants are propagated in 
this way. Budding is a 
process similar to graft¬ 
ing except that a bud is 
slipped into an incision in 
the bark, instead of a 
twig being inserted into Figure 259. -Whip OR Tongue Grafting. 

the end of a branch. In b the branch has been cut ex P ose 

. , , cambium in two places. In 2, the scion 

Layering IS a method been cut to fit the branch. In 3, the 
of obtaining new plants scion has been laid in place. In 4, the 

by covering a branch scion has been tied t0 the stock * In 5) the 
.,. . ,. J wax has been applied. 

with earth some distance 

from its tip. When roots form, the branch is severed from 
the main plant and transplanted. Roses, grapes, and 
currants are propagated by layering. All these methods 
are artificial, and seldom found in nature. 

Other plants propagate themselves by stems naturally, as 
the strawberry, which puts out long, leafless branches called 
stolons or runners, each stolon having a bud on the end which 
takes root when it finds favorable conditions, especially 
contact with the soil. When a new plant is well established 














272 


STEMS 


the stolon ceases to carry nourishment from the parent 
plant and soon dies. Black raspberries produce long, 
drooping stems which have buds on the ends similar to those 
on the stolons of strawberries. New plants are formed 
when these rest on the earth, several sometimes arising from 
the branching end of a parent plant, from which it later 
becomes separated. 

A large garden lily has a method of propagating itself 
that is not common, namely by bulblike growths produced 
in the axils of the leaves. 

Canada thistles, quack grass, and devil’s paint-brush are 
among the most difficult of weeds to eradicate owing to their 
branching, underground stems, each piece of which, when 
broken off by cultivation, forming a new plant. Dandelions, 
because of their greatly reduced stems, are not easily killed 
by trampling. In digging dandelions from lawns, care 
must be taken to cut deeply enough to remove the whole 
crown of the plant, otherwise the injured stem branches 
and forms a weed more troublesome than the original one. 

SUMMARY 

The stem is the part of the plant which forms the connec¬ 
tion between the roots which gather food materials and the 
leaves, where food is manufactured. It is compact and 
sturdy because it must bear the weight of the leaves- and 
branches, and because the vessels through which liquids 
are conducted in it must be well protected. Most stems 
grow above ground and upright, but some lie on the surface 
of the ground, and some below the soil. The stem of the 
woody plants is employed by man in more ways than any 
other part, furnishing him shelter, fuel, furniture, clothing, 
paper, parts of many machines and implements on which 
he is daily dependent. Stems are a source of some food 
for man and the stems of the grasses furnish food for 
many animals. 


REFERENCES 


273 


QUESTIONS 

What is the stem? What is its use to the plant? What positions 
do stems take ? How long do they live ? Name and describe the pecul¬ 
iar stems. What are vascular bundles? How are they arranged in 
a monocotyledonous stem? in a dicotyledonous stem? What is their 
work? What is meant by definite annual growth? indefinite annual 
growth? What are annual rings? How are they formed? 

REFERENCES 

• 

Bergen, Foundations of Botany, pages 62-129. 

Bergen and Caldwell, Practical Botany, pages 11-13, 39-103. 

jCoulter, Plant Life and Plant Uses, pages 49 and 143-193. 

Gibson, Sharp Eyes, pages 48-51, 240-243. 

Snyder, General Science, page 188. 



CHAPTER XX 


THE LEAF 

The leaf is the most important organ of the plant, for in 
it are carried on most of those processes which pertain to the 
life of the plant itself. Because it is so important an organ 
and because it has so many kinds of work to do, it has many 
adaptations in form, position, and structure which fit it 
to do its various kinds of work, besides giving individuality 
to plants. We shall study the work of the leaves first in order 
that we may more easily understand how the structure, form, 
and position of the various kinds of leaves adapt each to its 
work. 

237. The Work of a Leaf. — The life processes carried on 
by the leaf are (1) photosynthesis, peculiar to plants having 
chlorophyll, green coloring matter; (2) respiration, common 
to all living protoplasm; (3) digestion, (4) circulation, 

(5) assimilation, and (6) excretion. All but the first are 
much the same as the processes of the same names in animals. 
Transpiration which, like photosynthesis, is peculiar to 
green plants, while not one of the life processes, is made 
necessary by them. 

The work that a leaf does is of greater importance than 
anything else about it. We study its structure in order to 
understand how it is able to carry it on. For the same 
reason we study the arrangement of the leaves on the stem, 
and their form, which has a close relation to arrangement 
Although the work that leaves do for plants is the same in 
all kinds of plants the world over (with a few exceptions to 
be noted later), each particular kind of plant has its peculiar 
shape, size, and arrangement of leaves. This helps us to 

274 








































Asa Gray (1810-1888) was born at Paris, Oneida Co., N. Y. 
He started out in life to be a doctor and took the degree of M. D. 
in 1831, but his main interest was in botany. Deserting the prac¬ 
tice of medicine, he took up his favorite study which was to make 
him the most famous American botanist of his time. 

After studying plants for a number of years, he became professor 
of natural history at Harvard, to which university he gave his re¬ 
markable collection of plants. 

Professor Gray was able to present technical facts in an inter- 
esting and simple manner. This helped to give a wide use to his 
numerous, scholarly textbooks on botany. His contributions to 
the science of botany were very important and gained for him in¬ 
ternational recognition. 

He never took a real course in botany but made plants his 
teachers. 

(Photograph used by courtesy of Harper and Brothers.) 





THE WORK OF A LEAF 


275 


distinguish one kind of plant from another and to describe 
and classify them. We need to know the meaning of certain 
terms used in describing leaves in order to read or to talk 
about them intelligently, so we must be familiar with those 
most commonly known. These can soon be learned by 
referring to the figures and explanations. 

In many ways, flowering plants are more intricate organ¬ 
isms than animals. Without the ability to change their 
environment, they must depend upon the soil as they find 
it, rich or poor, wet or dry, soft or hard, to furnish them 
water and such food materials as come to them in liquid form. 
Without being able to seek shelter, they must take sun or 
shade, heat or cold, rainy weather or dry, pure or impure 
air just as each comes. Lacking organs of offense or defense 
against other plants they must contend with them for mois¬ 
ture, air, and light, besides being subject to the attacks of 
organisms which injure them. In addition to making of 
themselves the best plants possible under the conditions, 
they must produce numerous offspring, furnish each new 
plant with a supply of food, and send them all out into the 
world to meet and to make use of such conditions as they 
may find. An examination of the plants in any garden or 
yard will show that varying degrees of success have been 
attained. In every case, however, it represents the best 
that could be done under the circumstances. When we 
consider that plants have not intelligence such as animals 
possess, it appears all the more remarkable that they can 
accomplish so much, often under very adverse conditions. 
The biologist’s great interest in plants is in the ways they 
adapt themselves to carry on their life processes under all 
sorts of conditions, as well as in the processes themselves. 
Those who raise plants can expect success only as they are 
able to supply the conditions under which each plant thrives 
best, and to control conditions and organisms which may be 
unfavorable. 


276 


THE LEAF 


A study of its leaves shows how a plant solves many of 
its problems. 

238. Parts of a Leaf. — The main part of a leaf is the blade. 
The petiole (Latin, petiolus, fruit stalk) is the part by which 
it is attached to the twig. This sometimes has small pro¬ 
jections called stipules at the base. 

239. Venation. — The leaf of most plants contains ribs or 
veins which determine its main form and serve to keep it firm. 



Figure 260. — Skeleton of Poplar Leaf. 

Note the epidermis still remaining on 
part of the leaf. Poplar leaves skeleton¬ 
ize very easily. This was picked up on 
the street. 



Figure 261. — Leaf 
of Elm. 


Simple leaf with a 
serrate margin and 
pinnately-netted ve¬ 
nation. Note that the 
leaf is asymmetrical 
at the base. The 
general shape is ovate 
oblong, with a sharp 
apex. 


There are two main types of arrangement of veins. The 
first, that in which there are a few veins of about the same 
size which run side by side without branching from the base of 
the leaf to the tip. These are the parallel-veined leaves found 
in grasses, lilies, and most other monocotyledonous plants. 
In the second type, the netted-veined leaves, a few main veins 
branch and divide, filling the spaces between them with a 






FORMS OF LEAVES 


277 



fine network of small veins. The main veins may have a 
palmate arrangement, as in the palmately-netted vein of the 
maple, or they may branch from a central vein, as in the 
pinnately-netted-veined leaf of the elm. In such a leaf, 
each branch of the mid-vein usually ends in a point of the 
margin, or in a notch. 

240. Forms of Leaves. — A -leaf is said to be simple when 
the blade is all in one part, and compound when it is divided 


Figure 262. — Palmately Compound Leaf of Woodbine. 

into three or more leaflets. The apple and the maple have 
simple leaves, the clover and the horse-chestnut have com¬ 
pound leaves. A compound leaf is pinnately compound 
when its leaflets branch from the midrib, as in the rose or the 
locust; ternately compound when there are three leaflets, 
as in the clover and oxalis, and palmately compound when 
there are five or more leaflets, as in the horse-chestnut and 
woodbine. Besides these general terms, the shape of the 
base of a leaf, the general shape of its blade, its tip, and 
its margin all have descriptive names which help us to 



278 


THE LEAF 


recognize any combination of them as belonging to a par¬ 
ticular leaf. For instance, the apple leaf is ovate-oblong, 
rounded or cordate at the base, with a serrate margin. A 
leaf with a blade as large as the combined surfaces of a com¬ 
pound leaf would be much more easily torn by the wind, 
and would cut off more light from the leaves below. Some 
leaves are very finely divided, being many times compound, 
like the carrot and the yarrow. 

PHOTOSYNTHESIS 

241. Definition of Photosynthesis. — The word photo¬ 
synthesis (Greek, phos, light; synthesis , composition) means 
putting together by means of light. It is the process of 
manufacturing carbohydrates from raw materials, a vital 
process performed only by green plants. 

242. The Process. — Many facts about this process are 
not well understood, but we can state a few with certainty: 

(1) that in the manufacture of carbohydrates by photosyn¬ 
thesis, carbon dioxide is used as one of the raw materials, 
the source of this gas being the air, in which it exists 3 or 4 
parts in 10,000, and the waste of the plant’s own respiration; 

(2) that another raw material used is water, which is taken 
up by roots; (3) that some oxygen is left over as a by¬ 
product and given off as a waste of the process of photosyn¬ 
thesis; (4) that chlorophyll, the green coloring matter of 
plants, is essential; (5) that light is necessary not only to 
develop the chlorophyll but also to enable it to manufacture 
carbohydrates; (6) that another necessary factor is a moder¬ 
ate degree of warmth. 

243. The Products. — Carbohydrates are the first visible 
product of photosynthesis, but proteins and oils result from 
later processes, probably very similar to photosynthesis, 
which take place in the green leaf. 

244. The Use Made of the Products. — The carbohy¬ 
drates, proteins, and oils thus made are used in three ways: 


THE IMPORTANCE OF PHOTOSYNTHESIS 279 


(1) some of it is digested in leaves and built up into new 
protoplasm; (2) some of it is stored in the leaves to be 
used later; (3) another portion is stored in other parts of 
the plant, as in the potato, in seeds, buds, and roots. 

Comparison . — The process of photosynthesis may be 
compared to any other manufacturing process which requires : 

1. A factory — in this case, green leaves. 

2. Machinery — the plant cells containing chlorophyll. 

3. Power — light from the sun, a form of energy. 

4. Raw materials — carbon dioxide and water, and small 
portions of nitrogen and other chemical substances which are 
dissolved in the water taken in by the roots. 

5. Working hours — daylight. 

In this comparison the products are the carbohydrates and 
other forms of food which are made from them, and the 
by-product, oxygen. This manufacturing process disposes 
of its products (1) by storing them on the premises, the 
leaf; (2) by using them on the premises, digesting them 
to make more protoplasm; (3) by sending them away to 
other parts for storage, or immediate use; (4) by using 
them to make other food substances, namely, proteins, and 
fats or oils. 

245. The Importance of Photosynthesis. — The impor¬ 
tance of photosynthesis cannot be overestimated. It is the 
only natural process in the world by which raw material can 
be changed into food and by which energy can be stored up 
for future use. The plant makes use of this stored-up energy 
to produce new leaves, flowers, etc. Animals, which have 
not the ability to manufacture food from raw materials, 
depend directly or indirectly upon green plants for their 
supply of food. Besides making all the vegetable food in 
the world, plants, in using the carbon dioxide produced by 
animals, keep the air free from excess of it and so make it 
safe for animals to breathe. They also, by the same pro¬ 
cess, keep it well supplied with oxygen. Photosynthesis is 


280 


THE LEAF 


the most important work of the leaf, as well as the vital 
process on which all other vital processes, both in plants and 
animals, depend. 

A second function of the leaf is to perform respiration. 
Respiration in plants is exactly the same as respiration in 
animals. That is, every living cell uses oxygen, combining 
it with some of its protoplasm, releasing energy for the work 
of the plant and forming carbon dioxide and other wastes in 
the process. Respiration is most easily studied in plants 
like toadstools which cannot perform photosynthesis, and in 
sprouting seedlings which have not developed chlorophyll. 

HOME WORK ON PHOTOSYNTHESIS 

Make a list of the plants that are used for food. Look up in an 
encyclopedia the amounts of each produced in a given year. Make 
a list of the industries which are dependent on agriculture. Obtain 
information concerning the number of men employed in each. 

What uses are made of starch and sugar aside from food? 

What are the sources of the protein used for food? Which of these 
depend directly upon photosynthesis? which indirectly upon it? 

LABORATORY STUDY 

To show that light is necessary for photosynthesis, fasten thin 
discs of cork to the upper and under sides of a leaf with clips, completely 
shutting off the light. Stand the plant in the bright light for half a 
day, then remove the corks from the leaf and the leaf from the plant. 
Heat enough 60 per cent alcohol to cover the leaf in a shallow glass 
dish. This may be done by setting the dish into hot water. Keep 
hot for half an hour, or till the chlorophyll is removed from the leaf. 
Turn off the alcohol and put drops of weak iodine on the leaf. Note 
that the circle covered by the cork discs show little starch or none, as 
indicated by the faint blue color or by lack of color. 

Make a similar test by comparing a leaf from a plant that has been 
in the dark twelve hours with one that has stood in the bright light 
for the same time, using alcohol to remove the chlorophyll and iodine 
for a test for the presence of starch, as before. 

To test the nature of the gas given off by growing algae collect a 
quantity of algae and place it in a deep glass jar in the sunlight. When 


ASSIMILATION 


281 


bubbles begin to show, place an inverted funnel over the algae. Fill a 
test tube with water and invert it over the upright stern of the funnel. 
When an inch or more of the gas has collected in the test tube, remove 
it carefully and thrust a glowing splinter into it. Increased brightness 
of the glow or bursting into flame shows that oxygen is present. 

246. Digestion of Food. — Although the plant manufac¬ 
tures food from raw materials, it cannot make use of it until 
it has been digested. The process of digestion takes place 
chiefly in the leaf and the digested food is carried to all 
parts of the plant which need it through the vascular bundles. 
There are many facts about digestion in plants which are 
not so well understood as this same process in animals. It 
is known, however, that the enzyme, diastase , which digests 
starch, is secreted by the protoplasm of the cells and that 
it is very similar to ptyalin, the ferment in the saliva of 
animals which digests starch. 

247. Circulation. — Circulation in plants differs from circu¬ 
lation in animals in not having any central organ for keep¬ 
ing the fluids in motion and in the substances which the 
vessels contain. The xylem of a vascular bundle (Figure 255) 
carries water taken up by the roots from the soil to the leaves, 
where it is combined with carbon from the air and built up 
into foods. The digested foods are carried from the leaf 
to the parts of the plant which need them in the phloem part 
of the vascular bundle, so that, generally speaking, we have 
an ascending stream of water in one part of the bundle and 
a descending stream of digested food in the other part. 
The term sap is used to include both. Sap is moved by the 
combined influence of osmosis (root pressure), transpiration, 
and possibly other factors. 

248. Assimilation. — This is the actual taking up by the 
plant cells of such parts of the digested food as they need. 
It is a building-up process which results in the growth of the 
plant till it reaches the stage of maturity and in maintaining 
it at that size. 


282 


THE LEAF 


249. Excretion. — Excretion in plants is the same as in 
animals in this respect that it is getting rid of material or sub¬ 
stances which are no longer of use to the plant. It very often 
happens, however, that these are not removed from the 
plant as in the case of animals, but are simply stored where 
they can do no harm. An example of this is the crystals 
of calcium oxalate which give to sorrel, or sour grass, its 
sour taste. The line between excretion and the secretion of 
certain substances, such as the oils in peppermint plants, is 
not easily drawn. In the case of the secretions, however, 
they often serve the purpose of preventing animals from 
eating the plants. 

250. Transpiration. — This is the process of evaporation 
which takes place in plants, water in the form of vapor escap¬ 
ing through very small openings in the leaves called stomata. 
It is not one of the vital processes but closely connected 
with them. Its only similarity to perspiration in animals, 
to which it has sometimes been likened, is that water is 
given off through openings in the outer covering of the plant. 
Transpiration is unavoidable because the roots of a plant 
usually take up more water than is needed for the vital 
processes, and because this excess accumulates in spaces 
which communicate with the outside through the stomata. 
The function of the stomata is to allow air containing ni¬ 
trogen to pass into the leaf, and excess oxygen to pass out. 
Incidentally, however, water passes out too. When transpi¬ 
ration is too rapid, the plant is deprived of needed water. 
Since transpiration is a menace to the well-being of a plant, 
numerous devices have been developed for regulating it. 
Thus: 1. The surface of a leaf is covered above and below 
by a layer of cutin, a transparent substance impervious to 
water, perforated only where stomata occur. 

2. The stomata are on the under side of the leaves in most 
plants, this position being less favorable to transpiration 
than the upper side. 


TRANSPIRATION 


283 


3. The stomata contain guard cells which regulate the 
size of the opening by absorbing moisture or losing it. When 
the guard cells are full of water, they are plump or turgid, 
leaving the stoma wide open. When they are soft or 
flaccid from lack of water, they collapse, partially closing 
the stoma. 

4. In addition to this regulating device the stomata may 
be under coverings of hair or wax to make evaporation less 
rapid, or they may be at the bottom of a very thick layer of 
cutin. 



Figure 263 . — Bit of Epidermis 
of Leaf. 

The dark structures are stomata. 
An area as large as a period on 
this page contains hundreds of 
stomata. 


5. A leaf may still further 
check transpiration by changing 
its position or by rolling its 
edges together. Corn leaves 
during a very dry period illus¬ 
trate this. 

6. Another device is seen in 
cactus plants which have a 
greatly reduced surface. The 
stem in these plants is green 
and it contains stomata, thus 
enabling it to do the work of 
leaves. 

7. The shedding of leaves in the fall is a device used by 
deciduous (de-sid'u-us: Latin, deciduus, falling off) trees to 
prevent undue transpiration. When the ground is frozen 
the roots are unable to absorb much water. If the leaves 
remained on the tree, water would be given off more rapidly 
than it could be gathered from the soil, resulting in damage 
to the plant. 

When the moisture in the air exceeds a certain quantity, 
evaporation does not take place readily, causing too much 
water to accumulate in the plant. To prevent damage 
from this condition, plants have modified stomata, called 
water pores, at the ends of the veins. These contain cells 




284 


THE LEAF 


which burst under pressure, allowing the water to exude. 
This process is known as guttation, and the drops so formed, 
as guttation drops. These are often seen in the morning 
on the ends of grass blades, and on the points of leaves that 
have serrate margins, like the strawberry. Guttation drops 
are sometimes absorbed by the plant and sometimes they 
evaporate, depending on the needs of the plant and the 
amount of moisture in the air, or, as we say, the degree of 
humidity. 

The amount of water that leaves a plant in a day by 
transpiration alone is very great. For example, a moderate¬ 
sized sunflower plant will give off a quart a day under 
ordinary conditions. 


LABORATORY WORK ON TRANSPIRATION 

Turn the under side of a geranium leaf or other large leaf so it lies 
against a cool window pane, holding it there in some way if necessary. 
After half an hour remove it and note the drops of moisture which 
resulted from transpiration. Try other leaves in the same way. 
Fasten a watch crystal to the under side of a leaf, using clips to hold 
it and vaseline to make the edges air tight. Do the same with the 
upper side of another leaf. Which side gives off moisture as shown by 
drops on the watch crystal? Plunge a large leaf into water and set 
in the sun. On which side do bubbles appear? Wait half an hour. 
What kind of gas do they contain? What process in the leaf pro¬ 
duced them ? If you cannot answer this now, try again after review¬ 
ing photosynthesis. 

Take three leaves from the same plant. Coat one on both sides with 
paraffine or vaseline, one on the upper side only and one on the lower 
side only. Lay them aside till your next laboratory period. Describe 
all three. Which is least wilted? Why? Lay them all aside till all 
are wilted, observing them now and then and making a record of what 
happens. 

Hold a leaf up to the light and notice the arrangement of the veins 
and the soft parts. 

Thoroughly water a fern or other plant growing in a jar. Cover 
the earth with tinfoil, oilcloth, or paraffine to prevent evaporation 
from the surface. Weigh it carefully, then let it stand on the scales, 




STRUCTURE OF LEAF (CROSS SECTION) 285 


adding weights from time to time to take the place of the water lost 
by evaporation. If the plant has large leaves, remove them; after 
the experiment is completed, draw their outline on cross section paper 
and find their combined surface. Compare it with the amount of 
water lost. At the same rate, estimate how much would be given off 
by a plant with a leaf surface ten times as great, or as many times as 
great as you please. Describe the whole experiment in writing, illus¬ 
trating with sketches or photographs, as you please. 

Cover a small fuchsia or balsam overnight with a bell jar. Where 
are the guttation drops found? Why dp they form there? Cover 
young plants of oats, wheat, corn, or grass in the same way. Where 
are the drops formed on them? Make drawings of one or more kinds 
of leaves used in this experiment. Write notes telling what you dis¬ 
covered. 

251. Structure of a Leaf (Cross Section). —While leaves 
vary greatly in number, size, position, and shape, the work 
that they do is very 
similar for each plant. 

A typical leaf is covered 
with a layer of thin cells 
called the epidermis. In 
hot, dry regions the epi¬ 
dermis has a heavy coat¬ 
ing of cutin, a substance 
which prevents evapora¬ 
tion. The epidermis on 
the under side of the leaf 
is thinner and has less cutin than that on the upper side of 
the leaf. It is pierced by many openings called stomata 
(Greek, stoma , a mouth) which allow the entrance of air and 
the exit of water and gas. Between these two layers of epi¬ 
dermis is the mesophyll (mez'o-fil: Greek, mesos, middle; 
phyllos, leaf) of the leaf, divided into two regions, (1) the up¬ 
per or palisade composed of slender, elongated cells placed 
side by side in upright position, (2) spongy layer consisting 
of rounded cells, loosely arranged with many spaces between 
them. 





ispongy layer 
-chlorophyll 


lower epidermis 


Figure 264 . — Cross Section of Bean 
Leaf. 

How many tissues present ? 





286 


THE LEAF 


Influences Affecting the Growth of Plants. — Experiments 
have already been performed showing that stems and 
leaves tend to turn towards the light (page 230), and that 
roots normally grow downward (page 230). The stimulus 
that causes roots to grow downward is gravity, and the 
response to this stimulus is geotropism (Greek, ge, earth; 
tropos , a turn). Response to the stimulus of light is known 
as phototropism (Greek, phos, light; tropos, a turn), while 
that of the sun is known as heliotropism (Greek, helios, sun; 
tropos, a turn). When roots turn aside to avoid an obstacle 
and when tendrils or climbing stems clasp a support, they 
are acting in response to the stimulus of contact, the root 
acting negatively and the tendril and stem positively. This 
response is known as thigmotropism (Greek , thigmos, touch; 
tropos, a turn). In general, plants or parts of them show 
positive thigmotropism towards stimuli that are helpful 
and negative thigmotropism towards those that are harmful. 
The roots of the elm and the poplar trees which force their 
way into sewer pipes through a joint and then fill it with roots 
are acting in response to the stimulus of the presence of 
water. This is known as hydrotropism (Greek, hydros, 
water; tropos, a turn). 

LABORATORY STUDY OF LEAVES 

Draw a leaf of geranium (or other plant). Label (1) blade, 
(2) petiole, (3) stipules, if any. Notice the arrangement of the veins 
as you look through it. 

Remove the leaves from an onion. Note the thickened bases and 
how they are attached to the short stem. 

Stand a stalk of celery in water tinted with red ink. Cut across 
it after two hours and observe the position of the vascular bundles. 
Trace them into the leaf. 

Pull off leaves of dock and plantain and observe the tough vascular 
bundles. 

Study a bit of epidermis with a microscope. Draw. Label stomata, 
epidermal cells, guard cells (2 around each stoma)/ Study a cross 
section. Label cuticle, outermost layer, epidermis (upper and under 


ADAPTATIONS OF A LEAF 


287 


surfaces), palisade layer under top epidermis; spongy layer , body of 
leaf; vein. Which cells contain chlorophyll ? 

HOME WORK ON LEAVES 

Pull up or cut off a large burdock plant. Measure the area covered 
by the lower leaves. What else grew in this area? What is its condi¬ 
tion? Why? Do the same with plantain, dock, dandelion, knotweed, 
and other weeds in dooryard or garden. What plants form rosettes of 
leaves in the fall? 

Break off leaves of burdock, plantain, dock, and pieplant. Note 
the strings (fibrovascular bundles). 

Make a collection of leaves to illustrate the various kinds of shape, 
apex, margin, and base. 

Study the arrangement of leaves on the plants you see to determine 
how it is adapted to secure light for all the leaves. 

What effect does the wind have in helping or hindering leaves to 
get light? 

What happens when you make a “bag” from a leaf of live-for-ever? 

How can you tell guttation drops from dew? 

252. Adaptations of a Leaf. — The cutin of the epidermis 
prevents evaporation of water. The stomata allow air to 
enter and water and gases to pass out. Stomata themselves 
show many adaptations : (1) Position. In a leaf that extends 
horizontally from a plant, most of the stomata are on the 
under side, an adaptation which prevents their being closed 
by water. In leaves which float upon the water, the stomata 
are on the upper surface for the same reason. In plants with 
erect leaves, the stomata are distributed on both sides. 
In the cases of desert plants, the stomata are sunk below 
the level of the epidermis, or they are covered by hairs or 
wax, both of which tend to keep them from being filled with 
water and to prevent undue transpiration (evaporation). 
(2) The structure. This shows other adaptations. The 
opening is surrounded by two cells, called guard cells-, which 
have the property of absorbing water from the atmosphere. 
When these cells are full of moisture, they are plump or 
turgid; when they have only a little water they are flabby 


288 


THE LEAF 



or flaccid. The turgid guard cells leave the stomata wide 
open and allow free passage of air into the cell, and of water 
and gas out of it. Flaccid guard cells, on the other hand, 
make the opening small, decrease 
the amount of air that enters, 
and prevent undue evaporation 
from the inside of the leaf. Al¬ 
though each stoma is very small, 
they are so numerous that their 
combined action accomplishes a 
great deal. A square millimeter 
of the under surface of a lilac 
leaf contains 330 stomata, that 
of white birch, 237. 


FipuRE 266 .-—Peltate Leaf of 
Nasturtium. 

The petiole is attached at the 
middle of the back of the blade. 
The blade is orbicular, with en- 


Figure 265.— Leaves of Barberry. 


These leaves, all taken from the same tire margin. Note the twining 
bush, show the transition from normal petiole, a device for holding up 
leaves to thorns for protection. a weak stem. 


Most of the grasses show adaptations (1) in having very 
narrow leaves, fitted to grow close together; (2) in wavy 
edges if they are long, an adaptation which prevents their 
being torn by the wind; (3) in a clasping base, helping to 
strengthen the stem, and (4) in a collar /which prevents 
water from running down between the clasping base and the 
stem. 








PECULIAR USES OF LEAVES 


289 


253. The Arrangement of Leaves. — Whatever the ar¬ 
rangement of leaves on any particular plant, the object is to 
expose the leaves most advantageously to light and air, inci¬ 
dentally preventing their shading one another, which some¬ 
times causes a vertical branch and a horizontal branch of the 
same plant to show a different arrangement of leaves. In 
general, leaf arrangement falls into two groups: (1) small 
leaves arranged all along the length of a branch — the spiral 
arrangement, the simplest form of which is found in the elm 
where the leaves are in two rows alternating with each other; 
(2) a few large leaves at the end 
of a branch, as in the maple, where 
the leaves are in pairs, each pair 
alternating with its neighbors. In 
the first case the shape of the leaves 
is such that all the space is occu¬ 
pied without much overlapping; 
in the second, every leaf is fully 
exposed to the light by the lowest 
leaves having the longest petioles. 

(See Figure 269.) The leaves of 
a maple illustrate this. A rosette 
is formed by leaves, arranged spi¬ 
rally on a very short stem, with long petioles nearest to the 
ground, shorter ones alternating with them and filling the 
spaces. The dandelion, evening primrose, and thistle show 
rosettes. Light that has passed through one leaf is of little 
value to a leaf below it. Some plants have finely divided 
leaves, an adaptation which prevents any leaf shutting off 
all the light from those below. Angular leaves, round leaves, 
and leaflets are all adaptations to use up all the space with¬ 
out overlapping. 

254. Peculiar Uses of Leaves. — Some leaves, like the sun¬ 
dew, pitcher plant, and Venus’s flytrap, are adapted for catch¬ 
ing insects for the use of the plant as food (see page 366). In 





290 


THE LEAF 



others, as clematis, the petioles are used to help the plant in 
climbing. In the pea and grape, leaves have become modi¬ 
fied into tendrils which 
are used in helping the 
plant to climb. (See Fig¬ 
ure 270.) Still others 
have their leaves modi¬ 
fied to thorns for protec¬ 
tion, as in the thorny 
locust. 

255. Leafless Plants. 

— In plants like the cac¬ 
tus, already mentioned, 
the work usually done by 
leaves is performed by 
the stem. Asparagus is 
a, plant in which a much- 
branched stem serves as 
leaves, the true leaves 
being almost invisible 
scales. Another example 
is the plant commonly 
called smilax, in which 
the branches very closely 
resemble leaves. 

Other plants which 
have scales instead of 
leaves are dodder and 
Indian pipe, both of 

Figure 268.-Indian P.pe. which use food all ' Cad > r 

A saprophytic flowering plant. prepared. 

256. The Movement of 


Leaves. — Most movements of leaves are/due to unequal 
growth caused by the light being brighter on one side than 
on the other. Some leaves on this account “ follow the 








THE MOVEMENT OF LEAVES 291 

sun.” Others, like the compass plant, turn their edges to 
direct sunlight which is too strong for them. The clover and 
oxalis, which fold their leaflets at night, illustrate the so- 
called “ sleep movements” of plants. The movements of 
sensitive plants are due to the effect of the shock caused by 


Figure 269. — Leaves of Young Plants of Pokeweed. 

Note their large size, and their arrangement to prevent shutting off the 
light from those below. Contrast these leaves with those of Indian Pipe. 
This plant has mere scales in the place of large leaves, and they lack 
chlorophyll, the plant being pure white. It cannot manufacture food for 
itself, but depends on decaying organic matter in the soil. 

touching them. This causes the cells of an organ at the base 
of The petiole, called the pulvinus, to become soft and flaccid 
through loss of water which passes into the inter-cellular 
spaces, allowing the whole leaf to droop and the leaflet to fold. 

HOME WORK, MOVEMENTS OF PLANTS 

Place young seedlings in a window for a day. Which way do they 
turn? Turn the plants around and note how long it takes them to 
become erect; to become bent towards the window again. 



292 


THE LEAF 



On a sunny day set a stick parallel with the tip of a ragweed or other 
tall, slender weed. Set another stick about noon and another about 
three o’clock. Draw a diagram, or use your camera to show the changes 

in the position of the tip of 
the plant. Observe leaves of 
clover, and young daisy blos¬ 
soms. Do they change their 
positions with the sun ? What 
other plants do this? Does 
the age of the plant make any 
difference with its ability to 
change position? 

Bend a grass stem and 
fasten it flat. After a day 
or two observe its position. 
What changes have taken 
place? Remove the clasping 
leaf base and see what part of 
the stem was able to bend. 

Write notes telling what 
you have been able to observe 
in the cases above, and in any 
others which you may have 
noticed without being directed 
to do so. 


257. Economic Uses of 
Leaves. — The leaves of 
all the grasses as well as 
their stalks are used as 
food for cattle. Man uses 
for food the leaves of cab¬ 
bage, lettuce, spinach, 
celery, parsley, kale, kohl¬ 
rabi, and Swiss chard; 
and as a beverage, the 
leaves of the tea plant. The leaves of sofne of the mints, 
spearmint, wintergreen, peppermint, and sage, are used 
for flavoring, and the leaves of some plants, mullein, bone- 


Figure 270. — Pea Plant. 

The leaves are modified into tendrils for 
climbing. 






THE BLANCHING OF CELERY 


293 


set, catnip, peppermint, wintergreen, and wormwood, for 
medicine. 

258. The Blanching of Celery is a practical application of 
the fact that chlorophyll cannot develop in darkness. The 
stalks are either covered with earth, or the rows of celery 
are shut in from the light by long strips of black paper which 
allow only the top leaves 
to project into the light. 

The white leaves in the 
heart of a head of cab¬ 
bage, lettuce, or in open¬ 
ing buds in the spring 
are also accounted for by 
the fact that they are 
shut off from light by the 
leaves which surround 
them. 

SUMMARY 

The leaf is the organ 
of greatest use to the 
plant in performing the 
processes which maintain 
its own life. In the leaf 
food is manufactured, digested, and assimilated. Its cells 
carry on excretion and respiration to a greater degree than 
any other cells of the plant. 

The purpose of the shape, size, and arrangement of leaves 
is to enable them to get the greatest amount of light and air 
possible. 

On the process of photosynthesis depends the whole 
world’s supply of food. 

QUESTIONS 

Name the processes carried on by the leaves. Which is of the great¬ 
est use to man? Why? What is the object of leaf arrangement? 



Figure 271. — Vertical Section of 
Cabbage. 

The thickened bases of the leaves are 
used for food storage. The stem of a 
cabbage is short, and the bud very large 
in proportion. Note the buds in the axils 
of the leaves. 




294 


THE LEAF 


Describe the structure of a leaf. What two purposes are served by 
veins? Mention at least four plants that have peculiar leaves. De¬ 
scribe each and tell how it helps the plant. 

REFERENCES 

Bergen, Foundations of Botany, pages 130-177. 

Bergen and Caldwell, Practical Botany, pages 13-20, 39-103. 

Bergen and Davis, Principles of Botany, Chapters X, XI, XII. 

Conn, Biology, pages 114, 129, 135, 218. 

Coulter, Barnes, and Cowles, Textbook of Botany, Vol. I, pages 250, 
319-343. 

Curtiss, Nature and Development of Plants, Chapter I. 

Gager, Fundamentals of Botany, pages 26-46. 

Gibson, Sharp Eyes, pages 121-127. 

Snyder, General Science, page 193. 


CHAPTER XXI 



OTHER FLOWERING PLANTS 


259. The Flowering Plants. — True flowering plants are 
the most highly developed of all. They are numerous, 
it being estimated that there are 120,000 kinds. Some 
varieties are so small as 
hardly to be noticed, while 
others, like the hardwood 
trees, are very large. Some 
live submerged in water, 
while others are found 
only in deserts. 

The flowering plants are 
of special interest on ac¬ 
count of their intimate re¬ 
lation to our daily life, and 
on account of this close.re¬ 
lationship we should study 
some of the most common 
families, such as the grass, 
rose, mustard, and the 
like, all of which are easily 
recognized. 

The Grass Family. — The grass family has long narrow 
leaves with clasping bases and parallel veins, fibrous roots, 
and inconspicuous flowers which are pollinated by the wind. 
The grasses are the most important of all plants as food for 
man and the animals which he uses. This family includes 
corn, wheat, oats, barley, rye, rice, and similar grains. 
The corn plant was found growing in America when the New 

295 


Figure 272. — Walnut Tree. 





296 


OTHER FLOWERING PLANTS 


World was discovered, and it was one of the principal foods 
of the Indians. Now corn is grown wherever the season is 
not too short for it to come to maturity. 

Most of the work of planting, cultivating, and harvesting 
corn is done by machinery. Hand work is necessary 
only in removing the ears from the stalk and the husk from 
the ears. Because corn is so valuable a food for men and 

animals and because so much 
of the work necessary in 
raising it can be done by 
machinery, corn raising has 
become one of the most im¬ 
portant industries on the 
easily cultivated level 
prairies of the Middle West. 
Wheat and barley are men¬ 
tioned in the earliest litera¬ 
ture and were among the 
first plants cultivated for 
food. As men learned to 
till the soil and harvest these 
grains, agriculture became established and a marked step 
towards civilization was made. In China and India millions 
to-day depend very largely upon rice. 

An idea of the importance of the cereals as food crops can 
be gained from the following statistics as shown by reports 
in 1918. 


Rice, 

41,918,000 

bushels 

Wheat, 

918,920,000 

yy 

Oats, 

1,535,297,000 

yy 

Rye, 

76,687,000 

yy 

Barley, 

236,505,000 

yy 

Corn, 

2,717,775,000 

'yy 


These are for production in the United States alone. Cer¬ 
tain localities lead in the production of each grain. 



Figure 273. — Leaf of Oak. 

A simple leaf with a lobed margin. 






THE FLOWERING PLANTS 


297 


Lily Family. — Lilies have parallel-veined leaves. The 
flowers are made up of a six-parted perianth (calyx and 
corolla taken together), six stamens, 
and a three-parted pistil. The fruit is 
a capsule. Lilies are cultivated chiefly 
for decorative purposes. 

Walnut Family. — The trees of this 
family furnish us with nuts and valu¬ 
able lumber. The monoecious flowers 
(see page 204) are grouped in catkins. 

The leaves are alternate and pinnately 
compound (see page 277). All the 
walnuts and hickories belong to this 
very useful family (Figure 272). 

Beech Family. — Like the walnut 
family, this group consists of trees, of 
which the beech, oak, and chestnut are 
the most common. All are valuable 
for lumber and firewood. The leaves 
are simple, alternate, and straight- 
veined. The flowers are monoecious. 

Crowfoot Family .— 

This large family is val¬ 
uable to us for the medi¬ 
cines (mostly poisonous) 
which it furnishes. The 




Figure 274. — Siliques 
of White Mustard. 


medicinal members of this family are hydras- 
tis, aconite, hellebore, and larkspur; while 
other members, as clematis, peony, and colum¬ 
bine, are cultivated for ornament. The com¬ 
mon buttercup shows most of the character¬ 
istics of the crowfoot family. The leaves are 
commonly dissected; the petals, sepals, and 
pistil are all disconnected (see page 198). The juice of the 
buttercup is colorless and is biting to the taste. 


Figure 275. — 
Single Silique 
Split Open. 











298 


OTHER FLOWERING PLANTS 


Mustard Family. — Garden vegetables such as the turnip, 
radish, cabbage, horse-radish, and mustard belong to this 
family. All have regular flowers consisting of four sepals, 
four petals, and six stamens. The corolla is in the form of a 
Greek cross. These plants have a pungent, watery juice 
which is non-poisonous. The fruit is a kind of pod called a 
silique (see page 297). 

Rose Family. — The flowers are regular with the calyx 
usually of five sepals and the 
corolla of five petals. The leaves 
are alternate and usually serrate 
on the edge (see Figure 276). 

The rose family is as important 
in furnishing the luxuries of our 
food as the grass family is for 
supplying the necessaries. To 
this group belong all the common 
orchard fruits, such as apples, 
peaches, and plums, and many 
of the so-called berries, such as 
the raspberry and strawberry. 

Many of the members of this 
family are also cultivated for 
ornament. 




Figure 276. — Base of Com¬ 
pound Leaf of Rose, Show¬ 
ing Stipules. 


Figure 277. — Stem of 
Rose. 

The thorns which are 
outgrowths from the 
epidermis are adapta¬ 
tions for protection. 










THE FLOWERING PLANTS 


299 


Pulse Family. —Beans, 
peas, vetch, alfalfa, pea¬ 
nuts, clover, and the 
like are members of this 
family. These plants 
may be recognized by 
their irregular, papiliona¬ 
ceous flowers, alternate 
leaves with stipules (see 
Figure 292), and by their 
having the fruit in the 
form of a pod. This 
family furnishes us with 
most of our vegetable 
protein food. The plants 
improve the soil by the 
aid of bacteria. Wis- ^ IGURE 278 Nodules Caused by Bac- 

t ,! TERIA ON THE ROOTS OF BEAN PLANTS. 

tena, red bud, and the 

locusts are cultivated for ornamental purposes. 

Flax Family. — While 
this is not a large family, 
yet it furnishes all of our 
linen. Flax rarely grows 
wild, but requires culti¬ 
vation. 

Mallow Family .—This 
family is also important 
in furnishing material for 
our clothing, as the cot¬ 
ton plant belongs here. 
Hollyhock and althaea 
are forms cultivated for 
ornament. 

Parsley Family .—This 
family includes such gar- 



After the ovules are fertilized the piant 
pushes the pistils into the soil, where they 
mature. Note the nodules on the roots. 
The peanut is a dry, indehiscent fruit. 









300 


OTHER FLOWERING PLANTS 


den vegetables as parsnip, parsley, and carrots, and plants like 
fennel, dill, coriander, and caraway used for medicine and 
for flavoring food. These plants have hollow, ribbed stems, 
alternate, compound leaves, and flowers in an umbel (see 
Figure 201). 

Mint Family. — The members of this family are easily 
recognized by their square stems, opposite leaves with 



of Columbine. 

Showing spurred 
petals. Only a long- 
tongued insect can 
reach the nectar. 
Note the bunch of 
stamens upon which 
the insect alights. 



Figure 281. — Calla, a Flower with Spathe 
and Spadix. 

Representing a group of tropical plants of 
which Jack-in-the-pulpit is a common example 
in New York State. The spathe is a modi¬ 
fied leaf. 


crenate margins, and bilabiate flowers (an irregular flower 
divided into, two parts, see Figure 193). Peppermint, 
spearmint, catnip, horehound, pennyroyal, sage, savory, 
and thyme are some of the mints used for medicine and in 
food. 

Nightshade Family. — Here are found many poisonous 
plants, as tobacco and Jimson weed, from which stramonium 






THE FLOWERING PLANTS 


301 



(similar to belladonna but more powerful) is obtained. The 
tomato, potato, and egg-plant are used for food. Petunias 
are cultivated for ornament. The foliage of all these plants 
is rank-scented, the leaves are alternate, and the tubular 
flower five-parted. 

The Composite Family. — This family is typified by the 
common daisy and dandelion. They have their flowers in 


Figure 282. — Common Field Daisy. 

heads. These are of two kinds, ray-flowers and disk-flowers 
(see Figures 190, 191, and 192). This is one of the largest 
families of plants, and, from the standpoint of the botanist, 
the most complex. It contains our common weeds, such as 
daisy, dandelion, goldenrod, aster, burdock, thistle, and 
hawkweed. 

Not all the flowering plants are beneficial to man, and 
every farmer and gardener has to struggle with the weeds. 
Some of the members of the composite family, like the 
goldenrod and daisy, lend a charm to the fields, and many 



302 


OTHER FLOWERING PLANTS 


people dislike to think of them as obnoxious plants. But they 
prevent the grass from growing, and cattle will not eat 
them either in the winter or in the summer, so that they are 
a nuisance to the farmer. A weed, then, may be defined as a 
plant which interferes with the growth of some useful plant. 
Weeds are successful in growing and in living, because they 
have strong roots, produce many seeds, and have numerous 
devices for distributing their seeds. 

HOME WORK 

Consulting any maps which show where most of our common food 
plants are raised, make a note of the states which produce the greatest 
quantity of each. What is the leading industry in these states ? What 
industries are related ? Why ? Find pictures showing how some of these 
crops are harvested. What industries are concerned with manufactur¬ 
ing the products of these states ? What one in distributing the man¬ 
ufactured products ? By what routes are most of them shipped ? Why ? 
What are the leading crops in your township? in your county? in 
your state ? What foods do you have to bring from other states ? Why ? 
Try to think how climate, kind of soil, and the needs of the community 
influence the farmer as to the kinds of crops he plants. Notice what he 
does with the surplus. Find out from government reports how much 
grain was sent to Europe during the war. Find out how the number of 
bushels of grain produced' per acre compares with that in other coun¬ 
tries. Account for the facts you learn. How can a knowledge of biology 
help a farmer ? 

SUMMARY 

The flowering plants are the most highly developed of 
all the plants and bear an intimate relation to mankind. 
The many grasses and cereals furnish animals and man 
with much of their food. The cultivation of these plants 
has aided the development of civilization. 

QUESTIONS 

What plants furnished part of your food to-day ? In what part of the 
plant was this food made ? In what part stored ? What fruits do you 
eat? Which plants grow these fruits? Where do these plants live? 
Name plants, parts of which are used in medicine. What plants are used 


REFERENCES 


303 


in making paper? What parts of a plant are used in making houses? 
What kinds of cloth are made from cotton? from linen? from silk? 
from wool? What are the common weeds? 

REFERENCES 

Atkinson, Botany for Schools, Chapter XXXVIII. 

Coulter, Plant Life and Plant Uses, Chapter I. 

Encyclopedias. 

Geographies. 

Government Reports. 


CHAPTER XXII 


THE SIMPLEST GREEN PLANTS 

260. Introduction. — Many plants never have more than 
one cell and are so small that they can be studied only 
through a microscope. All these minute plants have long 
scientific names, often hard to remember, but they are the 
same names which the English, German, or Japanese chil¬ 
dren have to learn when they study these plants. 

The two plants discussed in this chapter belong to the 
group known as the Green Algce (Latin, algce, seaweed). 

The names of these two plants 
are Pleurococcus (plu-ro-kok'us) 
and Spirogyra (spi-ro-ji'ra). 

We are now to compare these 
microscopic plants with such larger 
plants as lily and nasturtium, each 
of which, composed of hundreds 
of cells, is able to respire, make 
its own food, and produce seeds. 

261. Pleurococcus. — Pleu¬ 
rococcus is a widely distributed, 
single-celled plant which grows in great abundance upon 
the shady side of trees, old buildings, and rocks. After 
a rain it is conspicuous in these places as green patches. 
A bit of this green substance examined with a microscope 
shows many green cells. Each plant or, we may say, each 
cell is a somewhat roundish structure with a clearly defined 
cell wall. The contents of the cell are green, due to the 
chlorophyll which conceals all parts of the cell except the 
nucleus. The nucleus usually lies near the center of the 

304 



a, single plant; b, plant divid¬ 
ing ; c, d, groups of plants. 




SPIROGYRA 


305 


cell. As long as the cell is full of chlorophyll, the cytoplasm 
cannot be seen (Figure 283). 

Pleurococcus makes its own food as larger plants do, and 
it is able to digest the starch and protein which it makes. 
Whenever a number of pleurococcus cells are examined, 
some are found to be dividing. In this division the nucleus 
forms two nuclei which move apart. A partition wall forms 
and two cells take the place of the old or parent cell. This 
method, called fission (Latin, fissus, cleft), is the simplest 
form of reproduction. It is a form of asexual or vegetative 
reproduction, as it takes place without the union of egg and 
sperm. In pleurococcus the cells do not always separate at 
once, but form groups of two, three, or more cells (Figure 
283). 

SUMMARY 

This simple unicellular (one-celled) green plant, pleu¬ 
rococcus, lives and makes its own food and produces new 
cells. While there are no flowers and seeds as in the plants 
already studied, yet this plant is able to reproduce itself. 
All the important life processes found in plants take place in 
the simple, single cell. 

LABORATORY STUDY OF PLEUROCOCCUS 

Study this as an example of a plant which consists of a single cell, 
but still performs all the processes common to complex plants. Soak a 
bit of bark and scrape it gently to get the pleurococci cells, some of which 
may be in groups. Place on a slide and examine with high-power 
microscope. Draw a single cell and a group of cells. Label cell wall 
and nucleus. 

262. Spirogyra. — This plant is best known as the “ pond 
scum v which grows in most fresh-water ponds and in slow- 
running streams. It may be kept for some time in glass 
dishes in a laboratory. Instead of being made up of round 
cells or clusters of cells, the cells of spirogyra are cylindrical 
in shape and are attached end to end. This results in long, 


306 


THE SIMPLEST GREEN PLANTS 


fine threads called filaments which float in the water in 
large masses. Spirogyra is only one of many kinds of fila¬ 
mentous algae. 

The individual cells of spirogyra are provided with one 
or more narrow green bands arranged spirally within the 



protoplasm. These spiral bands of chlorophyll are the 
special structures which manufacture food (Figure 284). 
The cells of the filament increase rapidly in size and divide, 

and thus the filaments 
increase in length. As 
each cell divides, the cell 
wall grows in at right 
angles to the length of 
the plank Spirogyra 
grows very rapidly in 
the spring. The bub¬ 
bles found among a mass 
of spirogyra contain the 
oxygen which the cells 
give off during photo¬ 
synthesis. 

During the summer there are times when spirogyra re¬ 
produces in another manner (Figure 285). Two cells of 
adjacent plants join by putting forth tubes which fuse on 
meeting. The contents of one cell pass through the tube, 
and flow into and unite with the contents of the other 



Figure 285. — Spirogyra Conjugating. 

A, zygospore; B, empty cell; C, canal 
formed by tubes ; D, tubes. 























ECONOMIC IMPORTANCE OF ALGM 


307 


cell. Thus there is formed a single roundish mass of proto¬ 
plasm surrounded by a thick wall. This mass of protoplasm 
is called a sexual spore, because two cells unite to form it. 
The two cells which thus unite are called gametes and are 
identical in all their parts. This spore, therefore, is known 
as a zygospore (Greek, zygos, yoke; spora , seed). In the 
formation of a zygospore, the cells are joined permanently and 
a simple form of sexual reproduction is present. 

As a zygospore, spirogyra can live in a resting condition 
during periods unfavorable to its growth, as in winter or 
during a drought. When conditions again become favor¬ 
able the zygospore germinates and grows into a filament. 
The spirogyra is able to do the same things which a pleuro- 
coccus does and has the same life processes. 

LABORATORY STUDY OF SPIROGYRA 

Notice: (1) the clear outer part called the cell wall; (2) the main 
mass of the cell, a substance called cytoplasm. (This can be easily seen 
by putting a 5 per cent sugar solution under the cover glass. The cyto¬ 
plasm draws away from the cell wall into a compact mass in the center 
of the cell.) (3) The darker portion, the nucleus, in or near the center of 
the cell. (This can be clearly seen by putting a drop of weak iodine 
under the cover glass, using fresh material for this test.) (4) A spiral 
band of green coloring matter, chlorophyll, containing bright spots. 

Examine spirogyra in a mass, floated out in water in a glass or on a 
plate. Feel it and observe that it is slimy. Note its color and deli¬ 
cacy. After it has been in the sun for a time, note the bubbles of gas 
entangled in the spirogyra, which help to make it float. With a micro¬ 
scope examine filaments which are joined in places by outgrowths from 
other filaments. Such filaments are said to be in conjugation. Draw 
the outgrowing tubes, the empty cell, and the zygospore or zygote. 
Label all. 

263. Economic Importance of Algae. — Although algae are 
so small they sometimes make trouble by causing the water 
stored in reservoirs to have a fishy taste and smell. This 
is due to substances formed during their rapid growth, not 
harmful, but unpleasant. A very small quantity of copper 


308 THE SIMPLEST GREEN PLANTS 

sulphate in the water kills the plants without making the 
water unsafe for drinking purposes. A canvas bag contain¬ 
ing crystals of copper sulphate is dragged through the water 
by men in a row boat. 

SUMMARY 

Both pleurococcus and spirogyra are called algae, and 
each' is typical of many other plants of the same kind. 
Our chief interests in them are that they are adapted to 
very simple conditions for living, and that each cell is 
capable of carrying on all the life processes for itself. Plants 
like pleurococcus are called unicellular; those like spirogyra, 
which consist of many cells joined end to end thus forming a 
strand, are called filamentous algae. Pleurococcus is found 
on old buildings, fences, posts, rocks, and on the bark of 
trees. It shows more plainly in wet weather than in dry, 
for then it is growing. Spirogyra grows in running water, 
attached to objects on the bottom, or floats in masses on the 
surface of ponds, ditches, and sluggish streams. Neither 
of these plants has any economic value, but some algae cause 
drinking water to have an unpleasant taste and smell. 

Algae are simple plants which grow in water or in moist 
places. Fresh-water algae are usually small. Algae illus¬ 
trate how a plant cell carries on the life processes. . The 
cell is the unit of plant structure, and plant cells are similar 
to animal cells in all essential respects. 

QUESTIONS 

What is a cell? Compare plant with animal cells. Explain the 
process of conjugation. In what respects is the formation of a zygospore 
similar to the process of fertilization in a flowering plant? 

REFERENCES 

Atkinson, High School Botany. 

Bennett and Murray, Cryptogamic Botany. 

Bergen and Caldwell, Practical Botany. 

Leavitt, Outlines of Botany. 


CHAPTER XXIII 


SMALLEST PLANTS (BACTERIA) 

264. Bacteria. — Bacteria are the smallest of all plants, 
— so small that they can be seen singly only through the aid 
of a powerful microscope. We do not know all about their 
life processes, but we have learned much about their effect. 
We constantly hear about these plants, either under their 
correct name, bacteria , or under the names of germs or 
microbes. Two incorrect ideas concern¬ 
ing bacteria are prevalent, — one, that 
bacteria are animals, and the other, that 
all are harmful. It is definitely known 
that bacteria are plants; that small as 
they are, they are among the most im¬ 
portant plants in the world; that most 
of them are helpful, and only a few harm¬ 
ful. They are, however, so much like 
the one-celled animals (protozoa) that 
the word germ is not unnaturally used 
to cover both. 

265. Shape and Size of Bacteria. — Bacteria, according to 

their shape, are grouped into three classes: (1) round 

(the cocci); (2) rod-shaped, like a short unsharpened pencil 
(the bacilli); (3) those that are shaped like a corkscrew 
(the spirilla). Most of the names for the different bacteria 
contain one or another of these words, thus indicating the 
shape of the bacterium 1 under discussion. The spirilla 
and. the bacilli often have on one or both ends tiny thread- 

1 Bacterium, singular of bacteria. 

309 



A, cocci; B, bacilli; 
C, spirilla; D, bacillus 
with flagella. 





310 


SMALLEST PLANTS ( BACTERIA) 


like hairs by which they move, giving the first observers 
reason to think that they were animal^ 

To show how small bacteria are, fifteen hundred of the 
rod-shaped form will hardly reach across the head of a pin. 
When bacteria are grown in the proper kind of substance, 
there are so many in a cluster that they appear as tiny spots 
or points, often tinged with a faint color. When seen alone 
under the microscope, they are clear, almost transparent, 
and colorless, and often have a bright, shining spot on the 
inside. 

266. Where Bacteria Are Found. — Bacteria are every¬ 
where, — in the air, as invisible dust; in the upper layers 
of the soil; and in water. We breathe in the microbes of 
the air with every breath, but generally with no injurious 
result. Every bacterium has its own work to do, and a 
healthy body gives little opportunity for most kinds of 
bacteria to do harm. 

267. Conditions Necessary for the Growth of Bacteria. — 

Like all other plants, bacteria must have all the proper 
conditions before they can grow and multiply. Their 
food is chiefly plant or animal matter, but they cannot 
make use of food except in the presence of warmth and 
moisture, and most of them require oxygen in addition. 
They get the oxygen from the surrounding air. 

268. Life Processes. — In the preparation of their food 
bacteria break up organic substances, that is, decompose 
them, causing the condition known as decay. They use 
some of the material resulting from decay; some they set 
free in the air; and the remainder is left on the earth to be 
used by more complex plants. In changing dead matter — 
plants, leaves, and animals — to a form which again becomes 
a part of the earth, bacteria perform a service valuable to 
man. 

Reproduction occurs in bacteria through simple, fission. 
Sometimes bacteria break entirely apart, while in other 


LIFE PROCESSES 


311 


cases they remain connected, forming a chain. Under 
favorable conditions each cell can grow to full size in half 
an hour and be ready to divide again. It is this ability 
to multiply rapidly which makes them of so great impor¬ 
tance, for a few hundred bacteria, even of the harmful 
ones, could produce little effect. 

In the process of growth, bacteria produce two sub¬ 
stances, enzyme (see page 14) and toxin (tox'in: Greek, 
toxicon, poison). Enzymes produce fermentation, a break- 
ing-up process of which man makes use to secure certain 
flavors and odors, as well as to soften hard materials. 
Toxins are usually poisonous to living organisms, including 
the bacteria which produce them. 

Enzymes cause the pleasant flavor of such articles of 
food as cheese and butter. The quality of tobacco depends 
largely upon the kind of bacteria which have been at work 
upon it. Such bacteria are classed as helpful, as are those 
which gather nitrogen for the plants of the bean family. 
Other helpful bacteria are those which make it possible 
for man to use sponges by ridding them of the soft, slimy 
substance with which they are filled when alive, as well 
as the bacteria which soften the useless parts of the flax 
plant so that the rest of it may be separated and made into 
linen. 

When food, air, warmth, or moisture is not sufficient, 
bacteria cease to grow and go into a resting state. That 
is, they change their form, and surround themselves with 
a substance which protects the soft protoplasm from being 
harmed by freezing, heating, or drying. The simple 
plants all do this, but the simpler the plant, the more 
easily does it resist. It is this ability to withstand un¬ 
favorable conditions and to resume growth when condi¬ 
tions change for the better that makes bacteria “ such good 
friends and such bad foes.” Our ability to control them is 
due largely to a knowledge of their habits. 


312 


SMALLEST PLANTS ( BACTERIA ) 


LABORATORY STUDY OF BACTERIA 

Prepare culture plates of agar-agar from the following formula: 
Agar-agar Formula for 1000 c.c. 


Agar-agar 1 
Beef extract 
Peptone 
Salt . . . 

Water . . 


15 grams 
3 grams 
10 grams 
5 grams 


1000 grams 


Boil material for the agar-agar formula; add sodium hydrate till the 
color of litmus paper is not changed; cool to about 56° C., and beat 
into this one whole egg, including the shell. Warm slowly to the boiling 
point and continue till the egg is firmly coagulated; then strain the clear 
medium through a cheesecloth on to moist cotton in a filter funnel. 

Work rapidly. Cool, and then boil once more. Filter through cotton 
into test tubes. Each tube should not be more than a quarter full. 
Plug the tubes with cotton. Then sterilize this mixture in the test tubes 
by placing them upright in water and boiling twenty minutes on each of 
three successive days. Let part of the test tubes cool, in a slanting 
position, having the plugged end elevated half an inch. These are called 
slant agar tubes. When petri 2 cultures are needed, melt up a sterile 
agar tube and pour into a sterile petri dish. 

1. To show that bacteria are present on one’s hands: draw the 
fingers of the unwashed hand across the surface of the agar-agar in petri 
dish; cover and set away for four days at room temperature or two 
days at body temperature. 

2. To show that fewer bacteria are present on freshly washed hands : 
draw the fingers of the washed hand across the surface of the agar-agar; 
cover and set away. 

3. To show that bacteria lodge under the nails, place on culture 
plates scrapings from under finger nails, (1) before washing the hands, 
(2) after washing the hands. 

4. To show that heating milk reduces the number of active bacteria, 
sprinkle drops of milk and water mixture on agar-agar petri dish, 
(1) natural milk, (2) pasteurized, (3) boiled. (Use one tenth milk 
and nine tenths sterilized water.) 

5. To show that bacteria change the medium in which they grow, 
note, besides the number, form, size, and color of the colonies, whether 
any change takes place in the agar-agar. 

6. To show that bacteria grow best in the presence of warmth and 
moisture, compare those grown under such conditions with those grown 

1 Secured at most drug stores. 2 Flat, round dish with cover. 








BACTERIA IN RELATION TO MILK 


313 


in a dry or a cold place. Note the influence (a) of warmth, (6) of cold, 
on the rapidity of growth. 

7. To show that bacteria are in the air, expose the surface of the cul¬ 
ture plate for a few seconds. 

8. To show that flies distribute bacteria, let a fly walk across the 
surface of the agar-agar in the petri dish. 

If bacteria have an opportunity, they work on every¬ 
thing which is capable of decay, so we need to know how 
to prevent their working upon food and other things which 
we do not wish to “ spoil.” Several ways in common 
use are: (1) cold storage, where there is not warmth suffi¬ 
cient for the growth of bacteria; (2) the use of salt and 
, other chemicals to prevent their getting a start, as in the 
curing and smoking of meat; (3) drying fruit and meat, 
thus removing water, a necessary condition for growth; 
and (4) heating fruit, vegetables, milk, etc., and sealing them 
in cans or jars while hot, thus killing any bacteria the 
substances may contain and keeping all others out. Any¬ 
thing prepared in this way is preserved by being made 
sterile or aseptic (Greek : a, not; sepein, to make putrid). 

269. Bacteria in Relation to Milk. — (See also Part III.) 
Milk as it comes from the healthy cow is practically free 
from bacteria of any kind. The number of bacteria present, 
however, is not of so much importance as the kind. But 
if a large number of bacteria are allowed to get into the 
milk, some of them are sure to be harmful and may find 
conditions so favorable for their growth as to make trouble 
for the person using the milk. 

A high grade of milk will not contain more than 500 to 
1000 bacteria per cubic centimeter. Such milk has been 
well cared for and comes from healthy cows. Some cities 
permit milk to be sold that contains as many as 100,000 
bacteria per cubic centimeter and some even more. Such 
milk comes from unhealthy cows or dirty barns, or has 
been kept too long, or has “ changed hands ” too many times. 


314 


SMALLEST PLANTS ( BACTERIA ) 


To deliver pure milk to the consumer costs the producer 
time, care, and money, and consumers should be willing to 
pay more for milk which has had proper care. 

Ice prevents harmful bacteria from multiplying sufficiently 
to make milk dangerous, unless 
the milk is kept too long a 
time. Preservatives, soda, borax, 
boric acid, formaldehyde, and the 
like, are sometimes used to pre¬ 
vent the growth of bacteria. In 
some cases no immediate harm 
seems to come to the persons us¬ 
ing milk thus preserved, but some # 
of these substances are poisonous, 
and pure milk, properly cared for, 
does not need them. So the use of 
any milk in which preservatives are found should be avoided. 

A harmless bacterium gets into milk kept too long and 
forms lactic acid, thus giving the milk a sour taste and 
causing it to curdle. Sour milk 
is perfectly wholesome for food, 
but the taste is disagreeable. In 
1857 Pasteur discovered this bac¬ 
terium. He also found that milk 
could be kept for several days 
without becoming sour, after it 
had been heated sufficiently to 
kill this bacterium. 

This process, called after its dis¬ 
coverer 'pasteurization, consists in 
heating milk for twenty minutes 
at a temperature of 60° C., or to a higher degree for a shorter 
time, and then cooling it rapidly. This procedure kills nearly 
all the bacteria in the milk and does not change the taste or 
make it hard to digest. Milk is not rendered absolutely 




Figure 287. — Beef Jelly. 
Exposed in unsanitary dairy. 







SOURCES OF DANGER IN MILK 315 


sterile, but it is a much safer food, especially for infants. 
At best pasteurization is only a corrective or precautionary 
measure, and we should demand that milk be kept clean and 
thus free from bacteria. 

Most raw milk products have their own forms of bacteria, 
nearly all of which are helpful. The flavor of June butter is 
imparted by a bacterium different from the one in January 
butter. So with cheese, each brand or flavor receives its 
taste through the action 


of a special bacterium. 

At every step in the use 
and manufacture of milk, 
it is necessary to know 
the conditions under 
which the helpful bac¬ 
teria work best, and how 
to keep out the harmful 
ones. 

270. Sources of Dan¬ 
ger in Milk. — The cow 

herself may be unhealthy 
and her disease trans¬ 
mitted through the milk. 

Of the several diseases 
which this animal may 
give, tuberculosis is the 
most common. Children are more liable than adults to 
take the disease in this way. There is no necessity to be 
in doubt about a cow’s being infected with tuberculosis, 
for in 1890 Koch discovered the tuberculin test, which 
enables the dairyman to detect the disease. This test is 
now commonly applied, and in some cities owners of herds 
which have been tested and found free from disease are 
allowed to sell their milk as “ certified,” though the mean¬ 
ing of this term varies. Not only is the raw milk from 


Figure 289. 

The metal cap keeps out dirt which can 
get by the paper stopper. 






316 


SMALLEST PLANTS ( BACTERIA) 


tubercular cows dangerous, but also the butter and cheese 
made from it. 

Bacteria multiply rapidly and remain active while milk 
is warm, consequently it should be cooled as soon as possible 
after it has been taken from the cow. Milk should not 
be used when it is too old, for in that case the harmless 
bacteria may all have died and harmful ones taken their 
places. Milk should not be left in a metal container, or 
open to the air, or placed in an ice chamber where it can 
absorb the odors of other foods. 

Ice cream should be eaten only when fresh, for poisons 
(ptomaines) are formed by the action of bacteria, especially 
in ice cream which has been melted and then refrozen. Ice 
cream should be made under clean and healthful conditions, 
and should never be exposed to the air of the street. 

271. Men Who Made the Study of Bacteria Possible.— 
The inventor of the microscope should be placed at the head 
of the list of men who made the study of bacteria possible, 
for without this instrument we should not know that such 
plants exist. We do not know who the actual inventor 
was, but the microscope was little more than a toy until 
it was improved by a Dutch naturalist, Leeuwenhoek 
(Lu'wen-hook), in the latter part of the seventeenth century. 
Next in the study of bacteria comes Pasteur, who discovered 
and studied them in their relation to the souring of milk 
and in other fermentations. Next comes Koch, who dis¬ 
covered a way of separating bacteria so that each kind may be 
studied by itself, a method called getting a “ pure culture.” 
He also invented the tuberculin test. Most of our facts 
about bacteria have been learned during the past thirty-five 
years, since men have learned how to prepare them for study. 

272. Healthy Bodies and Bacteria. — So much has been 
said about harmful bacteria that a word of caution is needed. 
Two facts should make us take a sane view of the situation: 
(1) for every harmful bacterium there are thousands of 



SUMMARY 


317 


helpful ones; and (2) harmful ones cannot do their work, or 
even live, in a perfectly healthy body, for such a body is 
constantly preparing a substance (antitoxin) which neu¬ 
tralizes the bacterial poison (toxin). Our chief aim, then, 
should be to keep well, and a few simple rules of hygiene will 
accomplish this. (1) Spend as much time as possible exer¬ 
cising in the open air. (2) Sleep as many as eight hours out 
of twenty-four in a well-ventilated room or out of doors. 
(3) Eat only food which agrees with you, and not too much 
of that. (4) Wear seasonable clothing. (5) Keep the skin 
clean through frequent bathing. (6) Have a definite occupa¬ 
tion, work faithfully at it, do your best, and don’t worry. 

SUMMARY 

The smallest and simplest of all the plants are the bacteria. 
Most of them are helpful, ridding the earth of waste material, 
giving flavor to food, gathering nitrogen from the air for 
plants, and aiding in the making of linen and sponges. Some 
bacteria are harmful and cause diseases in plants and animals. 
Bacteria are spherical, spiral, or rod-shaped. They are 
found everywhere, unless special pains have been taken to 
remove them. If they have plenty of food, air, moisture, 
and warmth, they multiply rapidly, and they go into the 
resting state, in which they can remain for a long time if 
any or all of the necessary conditions of growth are lacking. 
The harmful bacteria during their growth secrete a poisonous 
substance, toxin. When there are enough bacteria present 
to make a large quantity of toxin, the animal or plant host 
is made ill. Some bacteria, especially in the resting state, 
can bear freezing or boiling without being killed. In order 
to make anything “keep,” it is necessary either to kill all the 
bacteria by making the substance sterile or aseptic, or to put 
into it a preservative, a substance in which the bacteria 
cannot grow. We should use great care to avoid the bac¬ 
teria known to produce disease. 


318 


SMALLEST PLANTS {BACTERIA) 


Milk, one of' the most important articles of food, is a 
possible source of danger from harmful bacteria which may 
get into it in various ways. Milk should be kept cold, and 
should be used before it is too old. The harmless bacteria 
in milk form lactic acid and cause the milk to sour. The 
growth of these bacteria can be checked by pasteurizing the 
milk. Ice cream, if too old, is dangerous, for the slow- 
growing bacteria have had a chance to develop. 

The men who did the most to make the study of bacteria 
possible were Leeuwenhoek, who improved the microscope; 
Pasteur, who discovered bacteria in milk, and Koch, who 
found the way to make a pure culture and to test cows for 
tuberculosis. Many students are devoting their lives to 
the study of the various bacteria. 

Every one should know the main facts about bacteria so 
that he may not have a foolish fear of them, but may be 
able to take reasonable precautions against the harmful 
kinds. Since a healthy body is the best safeguard against 
harmful bacteria, we should observe the laws of hygiene in 
order to keep well, and at the same time avoid, when 
possible, the bacteria which produce disease. 

QUESTIONS 

What are the main points of likeness between a bacterium and 
a flowering plant? What has the pleurococcus which the bacterium 
lacks? How can food be protected from harmful bacteria? In what 
respects are bacteria harmful to milk? In what respects helpful? 
Why are a few harmful bacteria not injurious in a healthy body? If 
one bacterium divides every half hour, and all live, how many will there 
be at the end of twenty-four hours? (Solve by arithmetic or by 
algebra.) Why does an apple with a broken skin decay more rapidly 
than one in which the skin is not broken ? Why should one not put 
ice into water to cool it ? 

REFERENCES 

Calkins, Biology, pages 37-40. 

Conn, Biology, pages 26, 80, 232, 235. 


REFERENCES 


319 


Conn, The Story of Germ Life. 

Frankland, Our Secret Friends and Foes. 

Prudden, The Story of the Bacteria. 

Radot, The Life of Pasteur. 

Snyder, General Science, pages 209-218. 

U. S. Bulletin No. 56, Hygienic Laboratory Bulletin. Milk and Its 
Relation to Public Health. 

Woodhead, Bacteria and Their Products. 


CHAPTER XXIV 


FUNGI —PLANTS THAT LACK CHLOROPHYLL 

273. Fungi. — The Fungi are of importance to us be¬ 
cause : (1) some can be used as food (the so-called mush¬ 
rooms) ; (2) one of them, the yeast plant, is used in making 
bread, beer, and wine; (3) others spoil our food, as when 
they grow on bread and cake ; (4) they cause many diseases 
in plants. 

Fungi differ from most other plants in two respects. 
They are colorless, or nearly so, chiefly because they have 



Figure 290 . — Yeast Plants. 

A, single cell; B, cell with buds; C, group of cells; D, chain of cells. 


no chlorophyll. They are dependent for food on plant or 
animal substances, either dead or alive, because they lack 
chlorophyll and hence cannot make their own foods as the 
green plants do. 

Fungi which live on the substances or juices of live plants 
or of animals are called parasites (Greek, para, beside ; sitos, 

320 




THE YEAST PLANT 


321 


food), and those that live on dead plants or animals are 
called saprophytes (Greek, sapros, rotten; phyto, plant). 

274. The Yeast Plant. This plant is a unicellular fungus, 
too small to be seen by the naked eye. It is oval or almost 
round in shape, and nearly colorless. It has all the parts 
of a typical cell, although the nucleus cannot be seen without 
a special stain. Because it 
lives upon dead vegetable 
matter, it is a saprophyte. 

The Work of the Yeast 
Plant. — In the making 
of bread, we know that: 

(1) yeast secretes an en¬ 
zyme which breaks up 
sugar into simpler sub¬ 
stances; (2) in this pro¬ 
cess alcohol is formed and 
carbon dioxide is set free; 

(3) the yeast lives on the 
proteid substances in the 
flour; (4) both the gas 
which makes bread light 
and the alcohol are driven 
off by the heat of the oven 
when the bread is baked. 

Use is made of the en¬ 
zymes and yeast in the 
making of beer, ale, and porter. Before the action of bacteria 
and yeast were understood, much trouble was experienced in 
getting uniform products, owing to the presence of unde¬ 
sirable bacteria and yeasts. The possibility of making pure 
cultures, the use of the microscope, as well as the tests which 
are made in the laboratories at every step of the manufacture, 
have placed the industries of bread-making and brewing on 
a scientific basis. 



Figure 291 . — Fermentation Tubes. 


The bulb is filled with nutritive liquid 
containing yeast plants. As they grow 
they form carbon dioxide gas which col¬ 
lects in the bulb, forcing the liquid into 
the upright arm. These tubes are used 
in estimating the number of yeast plants 
in a substance and the rapidity of their 
growth. In water analysis, the forma¬ 
tion of gas with certain media indicates 
pollution. 



322 FUNGI —PLANTS THAT LACK CHLOROPHYLL 


275. Reproduction of the Yeast Plant.—The method of 
reproduction of the yeast plant is similar to that of the 
bacterium, but differs from it in that instead of dividing 
exactly in two, a bud usually pushes out from the side of 
the mature plant. Sometimes the second plant will form 



A , rhizoids; B, sporophores; C, stolon ; D, sporangia. 

a bud before it breaks away from the first, and so a chain 
is made. Often a single plant puts forth more than one 
bud (Figure 290). 

LABORATORY STUDY 

Prepare a Pasteur solution, a good food for yeast, as follows: 


Potassium phosphate .10 parts 

Calcium phosphate. 1 part 

Magnesium sulphate.50 parts 

Ammonium tartrate.50 parts 

Cane sugar. 750 parts 


Sufficient water to make a total of 5000 parts. (This may be used for 
the culture of other molds than yeast and also for bacteria.) 

Yeast. — Examine yeast cells under low power. Note their glistening 
appearance, and their number. Under the high power try to find all 
parts of a typical cell. Label and draw. Look for budding cells and 
chains of cells. Draw. Make a thick paste of water, yeast, and flour. 













OTHER FUNGI 


323 



Put an equal amount into each of three tumblers. Place one tumbler 
in a cool place. Into one of the remaining tumblers stir a teaspoonful 
of sugar and set both in a warm place. Examine several times a day 
and write down all the differences you ob¬ 
serve in the three mixtures. Try to give a 
reason for everything you observe. 


276. Bread Mold. — When ex¬ 
amined with the naked eye, bread 
mold appears like a thick mass of 
felt, made up of colorless, closely 
interwoven threads. These threads 
are called hyphce (hi'fe : Greek, hyphe, 
web) and are of two kinds, one lying 
on the surface of the bread or just 
below it, and the other standing up¬ 
right above the surface. The first 
are the nutritive hyphse, and the 
second the reproductive. On the 
ends of the latter are round black 
bodies which are full of spores, each 
of which is capable of producing a 
new mold plant, if it falls into a place 
where conditions are favorable for 
growth, — that is, where it has plenty 
of food, the right degree of warmth, 
and sufficient moisture. Other kinds Figure 293 .— Shaggy-mane 
of fungi may usually be found on a loaf 
of bread after a day or two, as spores 
of many kinds of molds are floating 
in the air at all times (Figure 292). 

277. Other Fungi. — A common fungus is the one that 
kills flies in the fall. At that time a dead fly is often ob¬ 
served on a window or mirror, the body surrounded by a 
whitish ring. Such a fly has been killed by fungus hyphae 
which have filled the body. The ring is composed of spores 


(COPRINUS COMATUS) IN 
Perfect Condition for 
Picking. (From Murrill’s 
“ Edible and Poisonous 
Mushrooms.”) 





324 FUNGI — PLANTS THAT LACK CHLOROPHYLL 


thrown off from the ends of the hyphse which have burst 
through thin places between the segments of the fly’s body. 

Other common fungi are potato blight, red rust of wheat, 
corn smut, which produces the black mass found in an ear 
of corn, and the bracket fungi, which grow in large numbers 



Figure 294. — Oyster Mushroom. 

An edible mushroom which grows on wood. (From MurriH’s “ Edible and 
Poisonous Mushrooms.”) 


on the trunks of trees and whose hyphse cause the death of 
the tree. 

The fungi used for food are nourishing, but there is a prej¬ 
udice against their use because other fungi which resemble 
them closely are poisonous. As a matter of fact, it is an 
easy task to learn to distinguish the edible from the poisonous 
fungi. While the harmless fungi are now used as food much 
more than formerly, only a few varieties are raised for trade 
purposes (Figures 294 and 295). 




LICHENS 


325 


LABORATORY STUDY 

Wet a piece of bread, put 
a tumbler over it, and set it 
in a warm place for three or 
four days. Examine without 
the microscope to get the 
general appearance. With 
the microscope note (1) the 
clear, colorless threads 
(hyphae) making up the mass; 

(2) the groups of spore-bearing 
bodies, black and round, on 
the ends of the upright stalks; 

(3) the spores coming out of 
them. 

Li- 



278. Lichens. 


Figure 295. — Common Field PUffball. 

This is in condition for picking when 
the inside is white. (From Murrill’s “ Edi¬ 
ble and Poisonous Mushrooms.”) 

chens (ll'kens) are grayish green plants which look like 
scales. They grow on old fences, rocks, trees, and the like 
and are especially noticeable after a 
rain. A lichen is made up of the 
hyphae of a fungus, which inclose the 
cells of an alga. The algal cells in a 
flat lichen are usually near the top 
and bottom, and the fungus is in the 
middle of the plant. The alga uses 
the moisture which the fungus collects 
and brings to the plant, and, by the 
use of its chlorophyll, makes food, a 
part of which is used by the fungus. 
The latter, after it has become ac¬ 
customed to the alga, cannot live 
apart from it, and the alga, while it 
can live by itself, appears plump and 
prosperous when it is found sur¬ 
rounded by fungal threads. The 
partnership, therefore, seems to be helpful to both plants. 
Such a relation between organisms is known as symbiosis 



Figure 296. — Bit of 
Lichen, Enlarged. 

A, fungal threads ; B, uni¬ 
cellular algae. 










326 FUNGI —PLANTS THAT LACK CHLOROPHYLL 

(sim-bl-o'sis, life together: Greek, syn, with; bios, life) 
(Figure 294). 

Lichens are interesting chiefly as representing this peculiar 
interdependence of plants. T^hey have little or no economic 

importance, although in 
the Arctic Regions they 
furnish a supply of food 
for the reindeer. The dye 
litmus is obtained from a 
lichen. 

We close the study of 
the simplest plants with 
the fungi. As in the case 
of the bacteria, men have 
spent their lives studying 
the fungi, especially those 
which cause disease. 
Much has been accom¬ 
plished, but a great deal 
remains to be done in find¬ 
ing out the cure for certain 
fungus diseases, especially 
those that attack vegeta¬ 
bles which we use for food. 

FIELD TRIP FOR THE STUDY OF LICHENS 

After a rainy period, examine trees, rocks, old fences, posts, and 
similar places for lichens. Note the form; the color; the kinds of trees 
having the greatest number of lichens; the trees having the smallest 
number, and the side of the tree having the greatest number. Make the 
same examination during a dry period. 

SUMMARY 

Fungi are plants similar in structure to the algae, but 
they lack chlorophyll. On this account fungi cannot make 
their own food, but always have to use that prepared by 




REFERENCES 


327 


another organism. As they lack chlorophyll, fungi cannot 
use carbon dioxide, and as a result that which they produce 
by respiration is cast off into the air, as is the case with 
animals and with green plants placed in the dark. 

The fungi which are most important economically are the 
yeasts used in making bread, or beer and other fermented 
liquors; the edible mushrooms; those that spoil food, as 
bread mold, and those which cause plant diseases, such as 
corn smut and wheat rust. Fungi reproduce by means of 
spores. The mutually helpful relation in which fungi and 
algse live in the lichen is called symbiosis. 

QUESTIONS 

What is the color of fungi ? Are they ever green ? Why not ? How- 
does their food differ from that of green plants? How does the yeast 
plant produce changes in flour? How does the work of bread mold and 
yeast compare with that of a green flowering plant ? What are lichens ? 
Do lichens grow equally well on all sides of a tree ? on all trees ? How 
do they appear when wet? when dry? What colors do you find 
among them? 

REFERENCES 

Atkinson, High School Botany. 

Atkinson, Mushrooms. 

Bennett and Murray, Cryptogamic Botany. 

Cook and Berkley, Fungi. 

Gibson, Our Edible Toadstools and Mushrooms. 

Marshall (The Nature Library), Mushrooms. 

Trouessart, Microbes, Ferments, and Molds. 


CHAPTER XXV 


MOSSES AND THEIR ALLIES 

279. General Features. — The plants in this group have 
more parts, stems, leaves, etc., than the fungi and algae 
have; the chlorophyll is evenly distributed, and they tend 
to grow erect. The life history of the mosses is more com¬ 
plex than that of the simple algae 
(Figure 299). 

If a cushion of moss is ex¬ 
amined, it is found to be made 
up of small plants packed closely 
together. At certain times of 
the year some of these plants 
have a stiff, wiry, brownish stalk, 
surmounted by a boxlike capsule, 
on top of which may be a shaggy 
cap or cover (Figures 298 and 
299). 

280. Habitat. — Mosses grow 
A , calyptra ; B, capsule; C, seta; i n moist places, for their root- 
A female gametophyte. uke rhizoidg ^ ^ gufficiently 

developed to gather water from the soil. They thrive best 
in shady woods, on decaying logs, and on stones wet by 
spray. Another reason for their need of moisture will ap¬ 
pear in the study of their reproduction. 

281. Life History. — If a dry moss capsule is shaken, 
powdery spores, much like the “ smoke ” from a puffball, 
float off in the air. When these spores fall on moist ground, 
each sends out a small, alga-like thread which branches, 

328 



Figure 298. — Types of Moss. 



LIFE HISTORY 


329 


forming a tangled mass called the protonema (pro-to-ne'ma: 
Greek, protos, first; nema, thread). These threads pro¬ 
duce buds from which leafy moss plants grow. The latter 
produce gametes (reproductive cells which unite to form a 
new organism) and so these moss plants are called gameto- 
phytes (gamete plants). 


The gametes are of two kinds, eggs (large non-motile 
cells) and sperms (motile cells). The egg cells are produced 
in special vase-shaped organs called archegonia (ar-ke-go'ni-a), 
and the sperm cells in other organs called antheridia. When 
moss plants are repro¬ 
ducing, both of the re¬ 
productive organs are 
found surrounded by 
sterile hairs at the top 
of the stems. Some 
mosses have both an¬ 
theridia and archegonia 
on the same plant, while 
other mosses have only 
one kind on each plant. 

The moss plant which 
bears the antheridia re¬ 
mains short and has on the top a rosette of leaves, in the 
center of which is the sex organ. The plant which bears 
archegonia usually grows tall after the egg cells have been 
fertilized. 

Many sperms come from each of the antheridia. These 
move by the use of cilia when water is present, a film of 
dew being sufficient. The female moss plant has on its 
upper end one or more archegonia, each of which contains 
an egg cell. When the egg is ripe or ready To be fertilized, 
sperms may swim to it if water is present. A sperm enters 
the archegonium and fuses with the egg cell, thus forming a 
sexual cell, known as the fertilized egg cell. 



Figure 299 . 


Diagram of Life History 
of Moss. 







330 


MOSSES AND THEIR ALLIES 


From this fertilized egg cell a sporophyte (spore plant) 
grows out of the archegonium. The sporophyte consists 
of a foot, a pad by which it gets its food from the gameto- 
phyte, the seta, a slender stalk, and the capsule or spore- 
case. While every mature gametophyte leads an inde¬ 
pendent existence, the sporophyte is a parasite. 

Thus in its life history the moss plant has two distinct 
generations, the gametophyte or sexual and the sporophyte 
which reproduces asexually (Figure 299), by spores! This 
is known as the alternation of generations. That is, a 
sexual generation produces an asexual generation and an 
asexual in turn produces a sexual generation. 

282. Economic Value. — Mosses have little economic 
value. In cold regions some kinds are dug from under 
the snow to be used as food for the reindeer. They are 

interesting as showing a stage of de¬ 
velopment of the flowering plants. 

LABORATORY STUDY 

Moss (Polytrichum). Study moss plants 
and note the difference in size between the 
male and female plants. Make a drawing to 
show the difference in size and in the arrange¬ 
ment of the leaves. Select a female gameto¬ 
phyte which has a sporophyte. Draw and label 
the seia or stalk, and the capsule, the box at the 
top. Look for moss plants on trees, along the 
edges of sidewalks, and on damp soil. With 
the microscope examine archegonia and an- 
theridia. Draw and label. When antheridia 
from fresh material are used, the sperms can 
usually be seen escaping from the antheridium. 

283. Marchantia. — Marchantia (mar-kan'tia) is a plant 
belonging to the moss group, which grows in very moist places. 
It has a thin, broad body or thallus (thal'lus : Greek, thallos, 
a young shoot), which is green on the upper surface and 



CHANTIA. 

Plant with archegonial 
branches. 






MARCHANTIA 


331 


brown or gray on the under 
side. In the middle of the 
thallus is a midrib. On the 
upper surface are diamond¬ 
shaped markings, each of which 
has an opening which leads to 
an air chamber below. On the 
under side are rhizoids, which 
attach the plant loosely to the 
soil. 

The liverworts, which are 
well represented by marchantia, 
are adapting themselves to a 
life on land, but they are still 
dependent upon water. Their reproductive habits are like 
those of the mosses (Figures 300 and 301), but the sporophyte 
generation is less conspicuous. 

LABORATORY STUDY 
OF MARCHANTIA 

Examine pieces of the plant 
and identify the thallus, mid¬ 
rib, rhizoids and markings. 
Examine the umbrella¬ 
shaped, upright branches 
which bear the antheridia or 
male reproductive organs, the 
branches with slender projec¬ 
tions which bear the arche- 
gonia or female reproductive 
organs. With a microscope 
examine a cross section of the 
thallus, and observe the open¬ 
ings and air chambers. 

SUMMARY 

Mosses are much more 
complex than algae and 



Figure 302.—A Common Liver¬ 
wort. 



Plant with antheridial branches. 





332 


MOSSES AND THEIR ALLIES 


fungi. Specialization is shown in the cells which gather and 
conduct water, the beginning of the absorptive and conductive 
systems of plants. There is also the beginning of a system 
for getting oxygen. The life history of a moss represents 
the alternation of generations, a generation which reproduces 
by spore (asexually), and one which reproduces by egg and 
sperm (sexually). The generation which bears spores is the 
sporophyte, and that which bears eggs and sperms, the 
gametophyte. 

QUESTIONS 

In what respects are mosses more highly developed than algae, fungi, 
and lichens? Why do mosses require so much moisture? Give the life 
history of a moss. 

REFERENCES 


Bergen and Caldwell, Practical Botany. 
Leavitt, Outlines of Botany. 

Smallwood, Textbook of Biology. 


CHAPTER XXVI 


FERNS AND THEIR ALLIES 

284. The Group. — The ferns are the best-known mem¬ 
bers of this group, but club mosses and rushes (horsetails) 
also belong to the fern family. The study of coal mines has 
shown us that ferns are very old plants and that they were 
formerly much more numerous than at the present time. 
The plants of this group 
have real stems, roots, 
and leaves, and most of 
them are larger than the 
mosses. While the ferns 
are not so dependent 
upon water as the mosses, 
they grow best in cool, 
moist woods and in rich 
soil. 

285. A Typical Fern. — 

The fern named pteris or 
bracken (Figure 305) is 
one of the best known 
and most widely distrib¬ 
uted. The stem proper 
is underground and lives on from year to year, while the 
part above earth renews itself annually. Some of these 
stems reach a length of ten or fifteen feet. They branch 
out and give off many fine roots. Leaves, termed fronds, 
form from the upper surface.of the stem and grow up through 
the soil into the air. 



Figure 303 . — Forked Veins of Fern 
Leaf. 


333 






334 


FERNS AND THEIR ALLIES 




Figure 304. — Cross Section of Stem 
of Pteris. 

A, epidermis; B, mechanical tissue; 
C. conductive tissue; D, fundamental 
tissue. 


The stem of the pteris 
fern is composed of well- 
defined clusters of cells 
which are grouped into 
tissues. These tissues 
are: (1) the epidermal 
on the outside, which 
protect the stem; (2) the 
fundamental, which make 
up the body of the stem 
and carry on most of the 
vital processes; (3) the 
mechanical tissues, vari¬ 
ously grouped, which by 
means of their thick-walled cells give the stem firmness; 
and (4) the conducting tissue, which is made up of several 
different kinds of cells, all of which carry liquids (Figure 304). 
The conducting tissue extends 
into the leaves and is the vein of 
the leaf. During certain seasons 
of the year, lines form along the 
margin of the under surfaces of 
the leaves. These lines are made 
up of many minute reproductive 
bodies, the sporangia (spor-an'ji-a: 

Greek, spore, seed; angeion, ves¬ 
sel). Each sporangium contains 
numerous spores. In some ferns 
the sporangia occur in dots, the 
sori (singular, sorus; Greek, soros, 
heap). (See Figures 306 and 307.) 

286. Life History of the Fern. 

— The fern plant just described 

forms spores in the sporangia. Figure 305.-Pteris, A Common 
These spores fall to the ground Fern. 









LIFE HISTORY OF THE FERN 


335 



Figure 306. — Diagram of Life History of Fern. 



O 

—Spores 


c 

Prothalltum / 



1 \ i*— New Fern 

! 

' " r ( 'T* 

1 / : /p W#ri — Attachment 

/ 

F-Protorrema \ / 

) ( °f Fern to 



■ / x//: /# m- Prothallium 

/ /m 

K Wtm 

f b / frt 


V f 11 IV 

• 1 /// k 


V |o 

Rhizoid / •' I 



Archegonia 

'■ Antheridia 



Figure 307. — Sporangia of Fern. 

A, incomplete ring of elastic cells; B, region of thin cells; C, stalk of 
sporangium; D, spores. 












336 FERNS AND THEIR I ALLIES 

and soon begin to grow. The sprout from the . spore is 
in the form of a single thread which is a protonema. From 
the fern protonema there develops a small, flat, heart- 
shaped body called the prothallium (Greek, pro, before; 
thallos, twig) which is indispensable to the life of the fern. 
On the under surface of the prothallium grow small bodies, 
the antheridia and archegonia. The 
antheridia produce numerous motile 
sperm cells, and each archegonium a 
single egg cell. A sperm cell, swim¬ 
ming about on the surface of a pro¬ 
tonema when it is wet, is attracted 
to an archegonium by a substance 
which is formed on it. This it enters, 
fuses with the egg cell, and forms the 
fertilized egg cell. Pro thallium is the 
name of the fern gametophyte. (See 
section 281.) 

When an egg cell is fertilized, it 
begins to divide and a new fern plant 
is soon formed. The young plant 
remains attached to the prothallium 
and gains nourishment from it. As 
soon as the young fern is able to get 
nourishment by its own roots, it 
begins life as an independent plant 
and the prothallium dies. There is 
the same alternation of generations 
in the fern that occurs in the mosses, the prothallium 
being the gametophyte and the “fern” the sporophyte, 
but the latter is the longer lived and much the larger plant 
(Figure 305). The prothallium is so small, in fact, that 
it is seldom noticed, while in the life history of mosses the 
green, leafy gametophyte is larger than the sporophyte 
and lives longer. 



Figure 308. — Equisetum, 
Fertile Stalk. 


A , sporangial cone ; B, 
collar of teeth; C, node; 
D, furrow; E, ridge. 




RELATED FORMS 


337 


FIELD TRIP TO GREENHOUSE OR 
WOODS TO STUDY FERNS 

Note the color of the plants, the character¬ 
istic fern leaf with its stipe or central stalk, 
its pinnae or leaflets, and also the method of 
unrolling from the base to the tip. Note the 
fruiting dots (sori) on the back of the leaves. 
In what kind of soil are ferns found? Do 
they grow best in the sun or in the shade? 
Do leaves remain green during the winter? 
Note the underground stem and its roots. 
Look for buds and young leaves. Note the 
forked veins. 



Figure 309. —Sporophyll 
of Equisetum (enlarged). 
A, sporophyll; B, spo¬ 
rangia ; C, spores. 


LABORATORY STUDY 



Examine the cross section of a stem and note the different kinds of 
tissue. Draw and label: (1) epidermal tissue on the outside; (2) mechani¬ 
cal , dark brown tissue in masses near the center; (3) conductive tissue , 

large openings; (4) funda¬ 
mental tissue filling the rest of 
the space. With a microscope 
examine the epidermis on the 
under side of the leaf, noting 
the shape of the cells and the 
stomata. Pull off a bit of 
the epidermis and try to dis¬ 
tinguish the green guard cells. 
Examine a sorus with low 
power of the microscope and 
see how it is made up of 
sporangia on stalks. 


287. Related Forms.— 

Club mosses, horsetails, 
and selaginella (se-laj-m- 
el'la) are plants which 
belong to the fern group. 
Club mosses bear their 
spores in a spike on 
scales which are modified 


Figure 310.— Equisetum. 

A, collar of teeth ; B, node; 

C, internode ; D, branch. 













338 


FERNS AND THEIR ALLIES 


leaves. In appearance these plants are more like mosses 
than ferns (Figures 312 and 313). 

Horsetail, or equisetum, grows in waste or damp places. 



Figure 311. — Club Moss. 

A, sporangial cone ; B, aerial 
stem ; C, roots ; D, underground 
stem. 


It has a hollow stem, with 
joints, a mineral coating on 
the outside of the stem, and 


Figure 312. — Equisetum 
or Horsetail, Sterile 
Branch. 













THE FORMATION OF COAL AND PEAT 339 


branches in a circle around each 
joint. The conductive tissue in 
this plant is arranged near the 
center of the stem (Figure 315). 

Selaginella is seldom seen in 
northern latitudes, except in 
greenhouses. 

288. Economic Importance. — 

The fern group, like the mosses, 
have little economic importance. 

The spores of the club mosses are 
used in making certain kinds of 
fireworks (especially those used 
indoors); also in drug stores to 
keep pills from sticking together. 

The plant itself is used in Christ¬ 
mas decoration. Horsetail, so named from its appearance, 
is a common plant in waste places. Another plant in this 
group was formerly cut, tied in bundles large enough to be 
held easily, and used for scouring woodwork or tinware, 
which accounts for its other name, 
the “ scouring rush.” 

289. The Formation of Coal and 
Peat. — Ages ago ferns were more 
numerous than they are now and 
many of them grew to be as large as 
our present trees. Geologists tell us 
that the climate was warmer and 
more moist than it is now, and condi¬ 
tions especially favored the growth 
of fern plants. Where these large 
ferns died and fell to the ground, great masses accumulated. 

As the earth’s surface changed, these masses became 
covered with soil or water, and under the influence of heat 
and pressure they, together with other plants (gymnosperms), 



A , spore equisetum ; 

B, elators. 



Figure 313. — Sporophyll (en¬ 
larged). 

A, sporophyll; B, sporangium; 
C, spores; D, spores (enlarged). 





340 


FERNS AND THEIR ALLIES 


changed into coal. At the same time natural gas and 
petroleum, or rock oil, were formed. No coal is being formed 
at the present time, and when our supply is exhausted 

we shall have to find other 
sources of heat and power. 

Peat, found in old bogs, 
consists largely of vegetable 
matter. When dried it can 
be used as fuel. 

SUMMARY 

Ferns and their allies are 
less dependent on water than 
are the algae, fungi, and 
mosses. They are more 
highly organized, as they 
have epidermis, stomata, me¬ 
chanical tissue, conductive 
tissue, stem, roots, and leaves. Their life history shows the 
alternation of generations, consisting of spore, protonema, 
pro thallium, and sporophyte. Club mosses, horsetail, and 
selaginella are closely related forms. Coal was formed from 
ferns which grew to the size of trees in regions which were 
then hot and moist. 

QUESTIONS 

What parts of the flowering plant are found in the fern? In an 
animal what corresponds to epidermal tissue? to conductive tissue? 
to fundamental tissue ? to mechanical tissue ? Compare the life history 
of a moss and a fern. Why can ferns do with less water than mosses? 
Illustrate by diagrams or sketches the life history of a fern. What 
plants are related to ferns? Tell how coal beds were formed. 

REFERENCES 

Bergen, Foundations of Botany, pages 277 and 286. 

Campbell, A University Textbook of Botany, pages 200 and 241. 

Curtis, A Textbook of General Botany, Chapters VII and VIII. 

Leavitt, Outlines of Botany, pages 198 and 204. 



Figure 315.— Cross Section of 
Stem of Equisetum. 

A , air passage; B, furrow; C, ridge; 
D, central air passage : E, vascular 
bundles. 







CHAPTER XXVII 


THE CONIFERS (GYMNOSPERMS) —FORESTS 

290. General Characteristics. — In passing from the ferns 
to the conifers, usually known as evergreens, we go from a 
lower to a higher order of plants. None of the algae, fungi, 
mosses, or ferns bear seeds, but all reproduce by spores or 
by fertilized eggs. Most of the evergreens are seed-bearing 
trees which vary in size, but which are alike in having trunks 
that taper from the base to tip without dividing. Such 
trunks are called excurrent , while the trunk of the elm which 
divides repeatedly is called deliquescent. (See Figure 316.) 
The conifer group contains the largest plants in the world 
and those which live to the greatest age. Their foliage is 
usually composed of dark green, needle-like leaves which 
remain attached to the tree for two or three years. Thus 
the trees always have some foliage and so are termed “ ever¬ 
green.” 

291. Pine Tree. — The pine illustrates the plants of this 
family. The pine has all the parts of a flowering plant 
— stem (trunk), branches, roots, leaves, seed-producing 
organs, and fruit (cones). 

Stem. — The trunk does not divide, — a marked character¬ 
istic of conifers. In a forest where trees are crowded to¬ 
gether and there is in consequence a struggle to get light, the 
trunks grow tall and most of the branches are near the top. 

A cross section of a stem shows a series of rings, known 
as annual rings, by which the approximate age of the tree 
can be told. In the spring when all the conditions are at 
their best and growth is rapid, the cells of the tree are 

341 


342 THE CONIFERS (GYMNOSPERMS) —FORESTS 

large and thin-walled, strength being sacrificed to size. 
In the fall or during a dry time in summer, the cells formed 
are much smaller and the walls thicker. These small cells 
which show most plainly make up the annual ring. During 
a season in which long, dry periods occur, more than one 
ring may be made. From the center to the bark extend lines 



Figure 316. — Conifers. 

Note the undivided (excurrent) trunk. 


which are made of pith and are known as medullary rays. 
The part of the stem where increase in thickness takes 
place is just under the bark. 

Branches. — The branches leave the stem almost hori¬ 
zontally and nearly in a circle around the trunk of the 
tree. In the pine they curve upward, but each kind of 
evergreen has its own habit of curvature in its branches. 




PINE TREE 


343 


Leaves. — The leaves, called needles, are long, slender, 
and flattened on one side. They grow in bundles of two, 
three, four, or five needles, 
according to the kind of 
pine. The leaves, which 
are borne but once in a 
place, remain on the tree 
from two to five years 
and then fall off, leaving 
the branches bare except 
near the ends. 

Roots. — The roots of 

% 

the pine vary according to 
the kind of pine and ac¬ 
cording to the soil, but 
they are always extensive. 

Seed-producing Organs. — Early in the spring, two kinds 
of strobili are found on the new shoots which grow from the 
terminal buds. One kind looks like short catkins, and they 

are borne in clusters near 
the base of the shoot. 
They consist of scales ar¬ 
ranged spirally around 
the central axis. Each 
scale bears two pollen 
sacs. These are the 
staminate strobili. They 
wither soon after shed¬ 
ding their pollen, al¬ 
though they may remain 
on the tree for a year. 
The other kind of strobi- 
lus is short and thick, and is found at the tip of the shoot 
or on the side of the shoot near the tip. This is the fe¬ 
male strobilus or carpellate cone, which like the staminate 



Figure 318. — Male Strobili. 

A, leaves of previous year; B, male 
strobili; C, new leaves. 



Figure 317. —Young Female Strobilus. 

A , strobilus; B, new leaves; C, leaves of 
previous year. 






344 THE CONIFERS (GYMNOSPERMS) — FORESTS 



strobilus already described is made up of scales arranged 
spirally around a central axis. Each scale near its base 
bears two ovules. When the pollen is ripe, each grain, be¬ 
ing provided with wing-like air 
sacs, is easily blown about by 
the wind. Some of the pollen 
sifts into the carpellate cone 
through the .spaces between 
the scales, which at this time 
are separated slightly. Then 
the scales close up, the cones 
turn downward, and continue 
to grow for several months 
(Figures 317-321). 

Fruit. — During the next 
year, the pollen grains which 
are shut up inside the scales 
put forth pollen tubes and 
fertilize the egg Cells which 
develop in the ovules. From 
the fertilized eggs the embryo 
pines develop. 

When the cones are about two years old the scales open 
and allow the seeds to drop out. Each seed is provided with 

a wing by which it is blown about, _ 

for the pine depends on the wind to 
scatter its seeds as well as its pollen. 

Because the seeds lie on the scale 
without being inclosed in an ovary, all 
these plants are called gymnosperms 
(Greek, gymnos, naked ; sperma, seed). 

292. Habitat. — The evergreens 
grow in sandy soil in temperate or 
in cold climates, but a few of them occur where it is very 
warm. The finest evergreen forests in the world are found 


Figure 319. — Mature Female 
Strobilus or Cone. 

A , central axis; B, scales (sporo- 
phylls). 


Figure 320. - Pollen 
Grain of Pine. 







RELATED FORMS OF CONIFERS 


345 


in the western part of North America, on the slopes facing 
the Pacific Ocean. 

293. Related Forms of Conifers. — Hemlocks, spruces, 
firs, and balsams have smaller, flatter needles than the 



a, arbor vitae ; b, hemlock. 

pines and they are not arranged in bundles. Cedars have 
scale-like leaves. Larch and cypress trees shed their leaves 
in the fall, but in other respects are much like the pines. 

FIELD STUDY OF GYMNOSPERMS 

Most of the work in connection with gymnosperms should be done 
out of doors. The student should learn to know by sight all the local 
native evergreens and those commonly planted for ornament. He 
should note the method of branching and the character of the trunk 
compared with other trees. He should observe the position of the cones 
on the branches and be able to give the reasons therefor. In the spring 
he should look for the male and female strobili, and for leaf buds in 
the winter. He should examine the leaf scars and the external rings 
which mark a year’s growth, and decide how many years each tree keeps 
its leaves. He should note the arrangement of the leaves on the 
branches, the annual rings in the wood and their relation to the grain 
of the wood, the resin on wounds, the curvature of the branches, and 
other features readily observed. 




346 THE CONIFERS (GYMNOSPERMS) — FORESTS 


STUDENT REPORT 



Needles 

Single 

Alternate 

Needles 

Scale-like 

Needles 
in Bundles 

Cones 

Large 

Cones 

Small 

Hemlock . 
White Pine 
Larch . . 

Cedar . . 

Spruce . . 

Etc. . . . 







LABORATORY WORK 

In the laboratory examine a cross section of the stem to see the dif¬ 
ference in the cells grown in the early and in the late part of a season. 
Note the pith and medullary rays. If specimens are available, examine 
sections of wood from different trees. Make a collection of the woods 
found in the vicinity. Examine scales from staminate and carpellate 
strobili. With the microscope examine pollen of pine. Draw and 
describe all. 

294. Economic Importance. — The value of the gym- 
nosperms can scarcely be overestimated. Most of the 
trees are sawed into lumber for building purposes, but 
some of them are used in their natural form for telegraph 
poles, masts of ships, and timbers of mines. Wood pulp, 
from which most of our paper is made, is produced from 
small spruce trees. The by-products of this group of 
trees are of great value. From the pine come tar, pitch, 
turpentine, and resin, while the bark of the hemlock was 
formerly extensively used in tanning leather. 

295. Forestry. — By forestry we mean the raising of 
repeated crops of timber on land unsuited for agriculture. 
An additional meaning that has come to be attached to it is 
the proper use of forest crops. This definition will make 
it plain that it is quite separate from agriculture, which is 
concerned principally with the crops which feed man or his 
animals or which furnish him material for clothing. It is 


















THE NEED FOR A STUDY OF FORESTRY 347 



also distinct from lumbering which has to do only with cutting 
and preparing the trees for market in whatever form they 
are to be used. 

296. The Need for a Study of Forestry. — We are using 
timber three times as fast as it grows. A study of a few 
minutes will show many 
of the uses to which wood 
is put which accounts for 
its great consumption. 

For instance, the paper 
on which you are writing 
was probably made from 
wood; the pencil which 
you are using is made 
largely of wood; the 
table on which you are 
writing is of wood; the 
floor on which the table 
stands is made of wood; 
the walls of the house, or 
some part of them, are 
made of wood; the cars 
in which the lumber was 


Figure 322. — A Virgin Forest of Mixed 
Hard Woods and Conifers in North¬ 
ern Pennsylvania. 

The splendid trunk in the middle ground 
is that of a cucumber tree. (Hugh P. 
Baker.) 


brought to your city were 
made of wood; the ties on 
which the rails rested over 
which the cars ran were 
made of wood; the chair 
in which you are sitting 
was made of wood. Not only are we dependent on wood for 
these many articles of daily use, but a system of water works 
depends for its success on the presence of woods or forests, 
(1) to insure a plentiful supply of rain, and (2) to hold it 
back so that it may produce a steady supply during the hot 
weather when rain does not fall often. Again, the covering 




348 THE CONIFERS (GYMNOSPERMS) — FORESTS 

of forests prevents the soil from being washed away, which 
results in two disadvantages, (1) the loss of the richest 
part of the soil itself, and (2) the stopping up of channels 
which might be used for transportation. Water thus held 
back by the porous soil of forests keeps rivers and lakes at 
a usable level during the whole season instead of having 
most of the water run off in a flood or freshet during the rainy 
season, causing destruction as well as wasting the water. 

Besides, forests, by acting as wind-breaks, often make a 
locality much more comfortable to live in, and some persons 
go so far as to say that the presence of a forest positively 
affects climate favorably, making a locality cooler in summer 
and warmer in winter. It is now well agreed that at least 
one fifth of the territory of a country should be wooded in 
order not only to have lumber enough to use, but also to 
secure the other benefits arising from forests, some of which 
are more important than the direct products of the forests 
themselves. 

297. Extent of Original (Virgin) Forest. — When the settlers 
came to America, the forest on the eastern coast extended 
for about a thousand miles inland from the Atlantic, reaching 
to the treeless prairies of the middle section. On the west¬ 
ern coast was a belt even wider extending from the prairies 
across the Rocky Mountains to the Pacific Ocean. 

The forests of the United States now cover about 550,000,- 
000 acres, or more than one fifth of the total area. 

“ Generally speaking, countries having over twenty per 
cent of woodlands have forest resources sufficient to supply 
their lumber industries and their firewood consumption, 
provided that such area is properly stocked and conserved.” 
— Schenck, Forest Policy, page 71. 

298. Attitude of the Early Settlers towards Forests. — 
The first care of the settlers was to provide shelter from wild 
beasts and from the hostile Indians, and their second care 
was to secure a supply of food to last over the winter. To 


FORESTS AND EARLY SETTLERS 


349 



accomplish both of these, the destruction of trees was 
necessary. Trees furnished the most abundant and the 
most natural material of which to build houses and to make 


Figure 323. —What Deforesting Is Doing in the United States. 

A scene in North Carolina showing the rapid removal of soil after the 
forest is cut. 

fuel, and they had to be removed before crops could be 
planted. Furthermore, they sheltered the settlers’ enemies, 
so it was a matter of safety to have extensive clearings around 






350 THE CONIFERS (GYMNOSPERMS) — FORESTS 

the houses. Besides, trees were so plentiful that there was 
no need to be careful about using them in any way. This 
attitude has been so thoughtlessly maintained that large 
tracts have been cleared for immediate profit or pleasure 
without thought of the future. Now the time has come 
when forests have to be conserved and additions made 


Figure 324. — What Deforesting Did in China. 

This represents the appearance of 200 square miles of once wooded moun¬ 
tains, which a century ago paid rich revenue on their lumber products. 

to them so far as possible, a condition which will be¬ 
come even more marked as the population increases and 
as the needs for wood and lumber become greater. Con¬ 
servation does not mean locking up the products of forests 
to prevent their being used, but seeing that they are properly 
used and providing for a future supply. Conservation has 
become necessary on account of previous extravagance. 
Formerly, when a settler had cleared the land so far from his 
house that it was a trouble to bring in wood, it was not a 




FOREST PRODUCTS 


351 


difficult matter to move to a new locality where there was 
still plenty of timber near at hand. 

299. Why the Forests Are Beneficial to the Soil. — We 
have already seen (page 256) that for the roots of a plant to 
be able to get their food from the soil it must be of such a 
nature that the roots can easily make their way through it, 
and it must be able to hold water between periods of rain. 
Trees help in this way, 
that when their leaves 
decay they form a part 
of the soil called humus, 
its most valuable part so 
far as furnishing the 
plants with food material 
is concerned. The de¬ 
cayed leaves have the 
property of making the 
soil capable of absorbing 
moisture and holding it 
as a sponge does. Inci¬ 
dentally this prevents 
floods and freshets, and 
also prevents the good 
soil from being washed 
away, or eroded. 

300. Forest Products. 

— Enough has been said 
to give some idea of the value of wood and lumber to the 
human race. A little thought will add greatly to our apprecia¬ 
tion of the uses of forests, some of which are incidental, but 
none the less valuable. In some localities, for example, maple 
trees are raised for the sugar and sirup which they produce. 
Chestnuts, hickories, walnuts, and others give us nuts year 
after year, as well as lumber when they are cut down. 
Willow trees give us a superior kind of charcoal used in medi- 



Figure 325. — Diagram Showing How 
Logs Are Quarter-sawn. 

A , slabs removed to square the log; 
B, C, short radial sections ; D, long radial 
sections. Note that at least one end of 
every section is oblique, and that some 
of the sections are very small, entailing- 
waste. Quarter-sawn lumber is used for 
furniture and interior finishing. 























352 THE CONIFERS (GYMNOSPERMS) — FORESTS 

cine and in making certain kinds of gunpowder : the poplars 
and basswood or linden give us excelsior, so useful in packing 
fragile articles and in making cheap upholstery. Turpen¬ 
tine, obtained from the pine trees, is used in paint and 
varnish. Thin sheets of the more beautiful kinds of wood 
are laid over the cheaper or less beautiful kinds in the form 
of veneer. Wood alcohol, so useful as fuel, is obtained from 
wood wastes, like sawdust and shavings. 

White pine was formerly the kind of pine most in demand 
as well as the most abundant. Now yellow pine is taking 

its place on account of the 
scarcity and high cost of 
white pine, although yel¬ 
low pine is slightly in¬ 
ferior. White oak is 
highly valued for interior 
finishing, floors, and furni¬ 
ture. Maple has a fine¬ 
grained, hard wood which 
is much prized for furni¬ 
ture and other purposes. 
Curly maple and bird’s- 
eye maple are valued as 
wood for veneer. The 
former has a wavy grain, and the latter has numerous glisten¬ 
ing points scattered through it, thought to be undeveloped 
adventitious buds. Black walnut, cherry, and mahogany are 
valuable for furniture. Hickory, elm, and ash are used for 
handles of tools and for parts of vehicles where toughness is 
required. Applewood, holly, and box are sought for turned 
articles. Cedar, larch, and cypress are used for posts and 
poles, and basswood for trunks and crates on account of its 
toughness, lightness, and elasticity. Poplar and catalpa are 
planted where shade is desired in a short time, on account 
of their rapid growth. 







PRESERVATION OF WOOD 


353 


The part of a tree nearest the center is called the heart- 
wood, and that outside of it the sap-wood. Heart-wood is 
often of a different color from sap-wood, due to substances 
deposited in the cell-walls when they become old. For many 
purposes, heart-wood lasts longer than sap-wood, especially 
in posts or timbers used under ground. Charring the ends 
of posts put into the ground increases their durability. 

301. Preservation of Wood. — There are great differences 
in woods as to their ability to last in the soil or under water. 



Figure 327. — Nursery Where Young Trees Are Started. 


Some, like cypress, cedar, and locust, have the ability to 
withstand decay on account of substances contained in the 
wood, such as resins. All wood lasts longer if it is seasoned, 
that is, allowed to dry out in the air before being used. 
Wood that is to be used in damp places, however, usually 
needs treatment to prevent or at least to retard the process 
of decay. As decay is caused largely by the work of bacteria 
or of fungi, both of which depend upon moisture as one of 
their chief vital conditions, the use of timber thoroughly 



354 THE CONIFERS (GYMNOSPERMS) — FORESTS 


dried is one precaution taken to insure its lasting. Other 
methods used are charring portions that are to be covered by 
earth, and a third, the most common, is the use of chemicals. 
Railroad ties, for instance, are thoroughly impregnated with 
a solution containing creosote, among other substances, by 
being soaked in it for a long time, or by having it driven in 
under pressure. This acts as an antiseptic preventing 
bacteria and fungi from growing in the wood, and pro¬ 
longing the usefulness of the timber to a remarkable degree. 
While treating ties in this way is costly at first, it is an 



Figure 328. — Young Plantation in the Adirondacks. 

economic measure on the whole, as it takes a smaller quantity 
of timber, and less labor than would be the case if the ties 
had to be replaced frequently. 

Some kinds of wood depend for their beauty on the glisten¬ 
ing medullary rays. These show to best advantage when 
cut lengthwise or obliquely, an effect obtained in quarter- 
sawn timber. 

302. Properties of Wood. — The question may arise, What 
makes wood so valuable? Is there nothing else that can be 
used in its place ? One of its most valuable properties is 
that it is so easily shaped with sharp tools. Another is that 
it is light, compared with iron and steel, at the same time 




PROPERTIES OF WOOD 355 

being tough and elastic. It has remarkable resistance to 
crushing, twisting, and pulling apart. A piece of yellow 
pine one inch wide and thick and a foot long bears a load of 
720 pounds without breaking, when supported at the ends. 
It requires a weight of 17,300 pounds to pull it apart, and 
a load of 7400 pounds to crush.it. It is beautiful and 
it takes a high finish. The beauty of wood depends 


Figure 329. —Young Plantation 16 Years after Planting. 

much on its grain, the closeness of which and the hard¬ 
ness of the wood determining its suitability for particular 
purposes. For instance, where wood-cuts are to be made, the 
grain must be very small, and the wood very hard. Holly 
and box are best for this. In the case of wood used for fork 
and shovel handles, the qualities desired are toughness and 
smoothness. These are found in ash and hickory, and so 










356 THE CONIFERS (GYMNOSPERMS) — FORESTS 

the list might be lengthened indefinitely. Balsa wood, 
newly discovered in the tropics, is much lighter than cork. 
This is employed in making life preservers and rafts to be 
used in case of accident at sea. 

303. What Kinds of Land Shall We Use for Forests? — 
Generally speaking, that land which is so steep or so in¬ 
accessible that it cannot well be used for cultivating 
crops. This will depend largely on the locality. Conifers 
usually do better on poor land than do the deciduous trees. 


Figure 330. — Forest Fire in Montana. 

If the land is poor, planting any kind of trees will improve 
the quality of the soil. There are 10,000,000 acres of land 
in New York State unsuitable for agriculture, yet capable 
of growing beautiful and profitable forests. 

304. How Can Tracts Be Reforested? — The state will co¬ 
operate when large tracts are to be reforested. There are 
three ways, the use of any one of which depends on local con¬ 
ditions. Seeds may be gathered and sown broadcast, but 
this is expensive and wasteful, as most of the seed is lost by 






PROTECTION OF FORESTS 357 

falling on spots where it cannot grow, or is eaten by squirrels 
and birds. Again, it is not evenly distributed, and to 
obtain an even set requires additional work in transplanting. 
Better results are obtained the second way, namely, by 
planting the seeds evenly and covering them to reduce the 
number that may be wasted. This is nearly as costly, and 
not so satisfactory as the third method, which consists of 


Figure 331. — The Result of Hurricane and Fire in Idaho. 

planting the seeds and raising the young plants in nurseries 
till they are old enough to live in the open. Then they are 
set out under favorable conditions, in large numbers, and 
allowed to grow with only such care as disease or injury 
makes necessary. 

305. Protection of Forests. — Young forests, and old ones 
too* have their enemies. Fire, set by lightning or careless 
smokers or campers, fungal diseases, made possible by acci- 








358 THE CONIFERS (GYMNOSPERMS) — FORESTS 



dents or careless pruning, and insect enemies, require that 
forests have supervision and attention to prevent damage 
and consequent loss to the owners. The persons who watch 
over forests in this way are called forest rangers. 

306. The Work of a Forest Ranger. — A forest ranger has 
numerous duties, chief among which are to look out for fires 

and to report them when 
they occur. As a preven¬ 
tion, campers and others 
are cautioned to be care¬ 
ful about letting fire 
spread, stations or look¬ 
outs are maintained from 
which a large territory 
can be surveyed for signs 
of fire, airplanes are also 
used to this end, tele¬ 
phone lines are kept in 
repair to provide for 
calling help to fight fire, 
roads are cut for the same 
purpose, and also with a 
view of making it possible 
to check the spread of 
fire by removing all brush 
and other material which 
will burn. When fire 
occurs, it is fought by 
clearing paths across which it cannot travel for lack of 
fuel, and by digging trenches, which have the same effect. 
In some cases fires are beaten out with damp cloths or with 
branches of trees, and in rare cases, by the use of water. 
In some states regular trains are maintained on which are 
huge tanks containing water, and apparatus for throwing 
it some distance from the track. Prevention has proved 


Figure 332. —Castle Peak Fire Lookout. 
What is the advantage of this location ? 
From a National Forest in Colorado. 




iSSf 


Figure 333. — Sign Containing Warning about Fires. 

by human means, nearly all preventable; 952 were in¬ 
cendiary ; 1288 were caused by careless campers; and 1003 
by sparks from railroad locomotives, in violation of laws 
which call for spark arresters on engines used in or near 
the forests. 

Forest rangers also keep watch of the trees to see that 
fungus does not cause the death of trees,* and to prevent the 
spread of such diseases when they are found. In localities 
where cleared spaces in the national forests are rented for 
grazing purposes, forest rangers see that the regulations 
concerning the grazing of cattle are observed, collect fees, 


THE WORK OF A FOREST RANGER 359 


more effective than any kind of device, however, and most 
.efforts are being made in that direction. Signs and posters 
warn persons to be careful. 

Campers are taught how to select a spot for a fire, how to 
care for it to prevent its being a menace, and how to put it 
out when breaking camp. 

Of the forest fires in the United States during 1917, 7814 
in number, 2132 were caused by lightning, and the others 




360 THE CONIFERS (GYMNOSPERMS) — FORESTS 


and otherwise serve as government agents. In some 
localities, the tract must be regularly patrolled to prevent 
the theft of valuable timber. 


YOU ARE CAREFUL 
WITH FIRE 

HELP TEACH OTHERS 


EXTINGUISH MATCHES, CIGARS, CIGARETTES 
PUT OUT YOUR CAMP FIRE BEFORE YOU LEAVE 


KEEP THE WOODS GREEN 

CONSERVATION COMMISSION 


Figure 334 . — Poster Warning against Fire. 

The life of a forest ranger requires good health and a love 
for the out-of-doors. It requires, too,. at least a common 
school education with special training to enable the ranger 






QUALIFICATION OF A FORESTER 


361 


to recognize fungal diseases, and to estimate the quantity 
of timber on a tract or the lumber in a tree. 

Scientific forestry is now practiced on about 90% of the 
public forests of the United States and on about 2% of the 
woodlands privately owned. Only about one fifth of the 
wooded area of the United States is under government 
control. New York State is taking steps to preserve her 



Figure 335. — Fire Train in the Adirondack^. 


forests and also to reforest large tracts which have been 
cut over (Figures 327-329). 

National Forest Reserves are maintained in 23 states, 
chiefly in the western third of the United States. In the 
eastern portion many of the states have preserves, and in 
addition there are a few privately owned preserves. 

307. Qualification of a Forester. — In addition to the prep¬ 
aration and qualifications necessary for a position as forest 
ranger, a forester must have much broader technical knowl¬ 
edge. This is usually gained by taking a course in a 





362 THE CONIFERS (GYMNOSPERMS) — FORESTS 

college of forestry, and by practical work in the forests under 
supervision. 

Forestry has long been practiced in Europe, but it is a new 
enterprise in the United States. As the necessity for it is 
seen and as more and more forest preserves are made, open¬ 
ings will occur as foresters for greater numbers of young men. 



Figure 336. — Fire Slash. 

The scene of a great destructive fire in 1908. 


There are two methods of obtaining revenue from forests, 
one known as clear cutting, in which all the timber is removed 
and the land cleared, after which it is again planted with 
young trees. This method has two advantages, one, that 
the timber is all about the same size, and the other that no 
trees need to be injured in removing some. Selective 
cutting, the second method, has this advantage, that the 
forest can be made to produce revenue continuously, but 




LUMBER 


363 


it has the disadvantage that in removing large trees, smaller 
ones are likely to be maimed or mutilated. Much depends 
upon the locality and the kinds of trees planted as to which 
kind of cutting is better. In both of these methods the 
forester is of great service. 

308. Lumbering. — This includes, primarily, cutting the 
trees, and getting them to the sawmill. Great waste has been 
characteristic of unscientific lumbering. This waste assumed 
two forms, injuring young trees in felling mature ones, and 
making use only of the most valuable part of the trees 
felled. The latter practice not only wastes much wood, that 
might be used in many ways, but it is also a menace to neigh¬ 
boring forests to have the dead, dry tops and limbs lying 
about to afford fuel for fire. When lumbering is done scien¬ 
tifically, injured young trees are pruned and treated so that 
they may not become diseased by the entrance of spores of 
wood-destroying fungi, and all parts of the trees felled are 
either made use of, or the less valuable are piled and burned 
under conditions which do not menace the safety of the re¬ 
maining trees and which leave a clean floor, one of the best 
possible protections against forest fires. 

309. Lumber. — Lumber includes all the forms of wood 
secured by sawing the trunk of a tree lengthwise. The log 
"is first squared by taking a slab, that is, the bark and the 
rounding part of the trunk beneath it from each side of 
the trunk. This is then sawed lengthwise, the shape and 
size of the sections determining the name as well as the 
uses to which the various pieces are put. So we have 
beams, planks, joists, lath, boards, etc. 

Lumber as it comes from the saw is termed rough lumber, 
being used chiefly for parts of buildings that are to be 
covered. Dressed lumber is prepared by smoothing the 
surface of rough lumber. The kind of tools used and the 
degree of smoothness produced depend on the use to be made 
of the lumber. 


364 THE CONIFERS (GYMNOSPERMS) — FORESTS 


310. Shade Trees. — When one has occasion to plant a tree, 
the question often arises as to what is the best kind of tree 
to plant. While much- depends on where the tree is to be 
planted, and on the care it will receive afterwards, there are 
a few general rules that may be kept in mind. For instance, 
elm trees, poplar trees, and silver maple trees have the bad 
habit of clogging waste and sewer pipes in their search for 
water, of which they demand a large supply. Besides, one 
should consider that silver maple trees are brittle and apt to 
split when they become old, and that their shade is light. 
Elm trees in some localities are subject to the attacks of elm 
beetles and require spraying to preserve them. Poplar 
trees are hard to kill when it becomes necessary to remove 
them, owing to their habit of sending up sprouts from the 
roots and from the stump. Horse-chestnut and catalpa 
trees make a great deal of litter, detracting from their useful¬ 
ness as ornamental trees. Other trees, like the Norway 
maple, have the habit of branching so low that they require 
frequent trimming in cities, to prevent their being in the 
way of umbrellas. The trimming is likely to mar their 
symmetry. Hard maple, oak, sycamore, ash, linden, and 
tulip are satisfactory trees for most localities, having all the 
good features and none of the bad ones of the other trees 
mentioned. It should be remembered in planting trees along 
paved streets that the conditions are very hard, and they 
should have special care, otherwise they will die from much 
cutting of the roots and branches, from the attacks of insects, 
and from the lack of food and water. In planting, trees 
should have space enough left between them so that each 
tree may grow on all sides. 

When it becomes necessary to trim a tree, care should be 
taken to saw the limbs off as close to the trunk as possible, 
and to cover the fresh wood with a coat of paint. This 
close cutting will enable the wound to heal readily, and 
the application of paint will exclude bacteria and fungi 


REFERENCES 


365 


which might otherwise gain entrance to the interior of the 
tree and cause injury or death. 

SUMMARY 

The conifers belong to a class of the higher plants. They 
have periods of active and less active growth, both together 
resulting in the appearance of annual rings. Because their 
seeds are not entirely inclosed in an ovary, but lie uncovered 
on a scale, they are called gymnosperms. Conifers are of 
great economic importance, for they supply much of our 
lumber, tar, pitch, and all our turpentine and resin. Forests 
help to regulate the flow of streams and they prevent the 
washing away of the soil. 

QUESTIONS 

How are gymnosperms like other plants? How do they differ from 
other plants? What kind of trunk is characteristic of gymnosperms? 
How does a tree which grows in a forest differ from one which grows 
in an open field ? Why ? What are annual rings ? How are they 
formed ? Describe the branches; the leaves; the roots; the strobili; 
the fruit. What is a sporophyte? Name the gymnosperms. Make 
a list of the uses to which lumber is put. What other products come 
from the evergreen forests? In what ways are forests beneficial? 
What are the governments doing to protect them? What regions in 
your own state are covered with forests? 

REFERENCES 

Gymnosperms. 

Bergen and Caldwell, Practical Botany, pages 390-411. 

Coulter, Plant Life and Plant Uses, pages 195 and 196. 

Forestry. 

Government pamphlets and bulletins. 

Hough, American Woods. 

Keeler, Handbook of Trees. 

National Geographic Magazine. 

Sargent, Trees of North America. 

Schenck, Forest Policy. 

Snyder, General Science, pages 263-269. 


CHAPTER XXVIII 


PECULIARITIES OF PLANT LIFE 

311. Unusual Plants. — In order to live, all plants must 
have conditions favorable to their vital processes, and 
many of them develop special modifications which aid them 
in the struggle for existence. Some of the modifications 
already studied in this book are the arrangement of leaves 
or the length of petioles to secure air and light; the presence 
of color, odor, and nectar, devices to attract insects and 
thus secure the pollination of flowers ; and the use of wings, 
pappus, and hooks to secure the distribution of seeds. Many 
of the carnivorous (Figures 337, 338, 339) and parasitic plants 

are remarkable for the 
modifications which make 
it possible for them to ob¬ 
tain nitrogen, an element 
lacking in the food supply 
of their particular en¬ 
vironment. 

The Pitcher Plant. —■ 
The leaves of this plant 
form a sort of vase which 
retains water in the bot¬ 
tom. When insects crawl into the leaf, their escape is pre¬ 
vented by hairs which grow around the opening on the inside 
and point downward, and the unfortunate victim, exhausted 
by his struggles to get out, falls into the water and is drowned. 
When the bodies decay, the plants secure the nitrogen which 
they are unable to get through their roots. 

366 



Figure 337. — Leaves of Pitcher Plant. 




UNUSUAL PLANTS 


367 


The Sundew. — This plant has round leaves covered 
with long glandular hairs which secrete a sticky substance. 
When an insect alights on a leaf, the hairs bend over and 
hold the victim until it dies, the secretions of the plant mean¬ 
while digesting the soft parts of the insect. When the leaf 
has absorbed this digested food, the hairs release the remain- 



Venus’s Flytrap: — This plant has another way to catch 
insects. The leaves end in a trap-like device in two parts 
which lie flat like the leaves of a book (see Figure 339). 
When an insect alights on one side, the other closes quickly 
and confines it by the interlocking hairs on the edges. 
Digestion and absorption soon take place, after which the 
leaves lie flat again, ready for another insect visitor. 




368 


PECULIARITIES OF PLANT LIFE 



Figure 340. — Cat-tails and Arrow-heads. 



Figure 341 . — Water-lilies — Hydrophytes. 








PLANT SOCIETIES 


369 


Indian Pipe. This plant, although it produces flowers 
and seeds, has no chlorophyll and so is a waxy white in 
appearance. It gets its nourishment from decayed organic 
matter, usually wood, just below the soil. A fungus which 
grows on the roots helps them to absorb this prepared food 
(see Figure 268). 

Mistletoe. — We are most familiar with this plant as a part 
of our Christmas decorations. Mistletoe has chlorophyll 
and so is able to manufacture its own food, but it has no 
roots for absorbing water, making it dependent on a larger 
plant for this necessary part 
of its vital conditions. The 
plant possesses absorbing or¬ 
gans which pierce the bark of 
the trees upon which it grows. 

As a result it does much in¬ 
jury to the trees by using the 
water which they need for 
their own life processes. In 
the South the mistletoe is 
regarded as a great pest. 

312. Movements of Plants. 

— Most plants move slowly 
and only in response to one 
of several stimuli. Touch, 
or contact, is the stimulus in the case of sundew and Venus’s 
flytrap, both of which are peculiar in moving quickly. 
Tendrils curve under the influence of the same stimulus, 
but they move slowly. 

313. Plant Societies. — The term plant society is applied 
to any collection of plants which grow under similar con¬ 
ditions. The trees of the forests, and the grass and weeds 
of our lawns, are typical examples. In most cases water, or 
the lack of it, is the basis for classifying or grouping plants 
in societies. Some plants, e.g., many algae, live submerged 



Figure 342. — Cross Section of 
Leaf of Desert Plant. 


Note the very thick layer of 
cutin (A)‘, the epidermal cells, also 
cutinized ( B) ; the short, incomplete 
layer of palisade cells (C); and a few 
cells of the spongy layer ( D ). Com¬ 
pare with Figure 263. 



370 


PECULIARITIES OF PLANT LIFE 


in the water, while others, like the waterlilies, live partly 
in the water, lifting their leaves and flowers into the air. 

Plants which live in the water are called hydrophytes 
(hy'dro-fites: Greek, hydor, water; phyton, plant). If 
such plants have roots, they are little more than holdfasts, 
for the hydrophytes do not need organs of absorption. 
Most of the members of this plant society are without 
mechanical tissue, for the water holds them firmly on all 
sides. The algae lack a conducting system as well, for 



Figure 343. — Sage Brush — Xerophytes. 


their source of food is all about them. Waterlilies get 
their oxygen and much of their carbon dioxide from the 
air through their leaves, which float on the surface of the 
water with the stomata on top. Air passages in the long, 
slender stems convey air to the roots which lie in the mud. 
Hydrophytes which lie under water have their leaves finely 
divided to offer as much surface as possible to the water 
and thus secure a full supply of oxygen. 

Plants which live in desert regions, of necessity, have to 
live on little water. They are called xerophytes (zer'o-fltes: 





PLANT SOCIETIES 


371 



Greek, xeros , dry; phyton, plant). Xerophytes usually 
have long roots so that when moisture is present they may 
gather it rapidly. Many forms have little surface exposed 
to the air; the branches are few, and there are no leaves. 
The stem, which is green in color, performs the work of 
photosynthesis. To conserve their water supply further, 
the xerophytes have a thick epidermis and few stomata (see 


Figure 344. — Giant Cacti — Xerophytes. 

Figure 342). These plants are an admirable illustration of 
making the most of what one has. 

Desert plants live in regions where it is usually both hot 
and dry, but plants of the Arctic Regions have many of 
the same modifications, only in a lesser degree. Much of 
the time severe cold prevents the roots from absorbing 
water, and the plant must keep what it already possesses. 
Some of the Arctic plants, therefore, have leaves which 
roll to reduce the surface and have, in addition, a coating 
of hairs, both devices for retarding transpiration. 




372 


PECULIARITIES OF PLANT LIFE 



Most of the plants which we see and which live where 
there are no great extremes of heat or cold and where it is 
neither wet nor dry are called mesophytes (mez'o-fites: 
Greek, mesos , middle; phyton, plant). They have few 


Figure 345. — Orchid. 

This plant lives in bogs. A habitat intermediate between that shown in 
Figures 340. 341, and 362. 

characteristics in common, but all have roots suited to the 
soil in which they gTow, and leaves which in shape and 
arrangement serve the purposes of each plant better than 
any others would do. Examples of this are the narrow, 




PLANT SOCIETIES 


373 



upright leaves of the grass, which grows thickly crowded 
together, the broad leaves of the trees, and the leaves of 
the ivy, which grows on walls, arranged like a mosaic. 
Many divisions of the mesophytes might be made, for some 
prefer sunny locations, others shady places, and so on. 

Plants which live in the air make up another group, 
called epiphytes (ep'i-fites: Greek, epi, upon; phyton , a 
plant) because they usually attach themselves to the stem 
of a larger plant. Their modifications consist of one kind 


Figure 346. — Long-spurred Violet, a Mesophyte. 

of roots for fixing them to their support and another capable 
of absorbing and storing water. The latter organs are called 
velamens and are composed of spongy tissue. They are 
situated on the outside of the plant, their work being to soak 
up rain and dew and conduct it to an inner region where it is 
used as the plant needs it. Velamens can also absorb moisture 
from the air. The epiphytes are characteristic of the tropics, 
where the air is full of moisture and where rains fall frequently. 
In our own part of the world, lichens have somewhat the 
same habit, and orchids in greenhouses are another example. 




374 


PECULIARITIES OF PLANT LIFE 



The study of plants which deals with their distribution 
and the factors which govern it is called plant ecology 
(e-kol'o-jy: Greek, ozkos, home; logos, talk). 


Figure 347 . — Mistletoe. 

A semi-parasite. This tree has no leaves. 

314. Plant Succession. — When a swamp is drained, a 
forest cleared, or a desert irrigated, plant conditions are 
changed. Thus it becomes impossible for some plants to 



SUMMARY OF OUR INTEREST IN PLANTS 375 

thrive in their former habitat, and possible for others to 
grow where before they could not. The replacing of one 
plant society by another is termed plant succession. When 
a forest is cleared and the tract burned over, the plant 
called fireweed appears in large numbers, even if a culti¬ 
vated crop is planted. After a year or two the fireweed 
gives way to a growth of 
blackberry and raspberry 
bushes, which are later 
replaced by grasses and 
weeds of various kinds. 

Another example of 
plant succession is seen 
in regions covered by 
fresh lava from a vol¬ 
cano. At first nothing 
grows. Probably bac¬ 
teria and fungi appear 
before other plants are 
noticed, but lichens are 
usually the first to be ob¬ 
served. These die and 
decompose, and their re¬ 
mains, together with bits 
of lava loosened by frost, 
wind, or water, accumu¬ 
late in depressions and 
form a soil in which 
mosses can grow. The 
remains of the mosses add to the organic matter in the 
slowly increasing soil, and, in the course of time, ferns and 
larger plants can grow. The last finally replace the mosses 
as they replaced the lichens. 

315. Summary of Our Interest in Plants. — Our first 
interest in plants is economic, that is, we think of them 



Sectional view of a branch infected 
with mistletoe, showing the relation be¬ 
tween the parasite and host; a, branch 
of host tree ; b, mistletoe ; c, primary 
sinker; d, sinker from cortical root; 
e , /, cortex of soft bark; g, cambium 
or growth ring; h, wood of branch. 
The starving and dwarfing of the branch 
beyond the mistletoe is shown at i. 






376 PECULIARITIES OF PLANT LIFE 


first in terms of their usefulness or harmfulness to us. As 
every animal in the world is dependent directly or indirectly 
upon plants for food, it becomes obvious to what a degree 
we are benefited by the ability of plants to make food out 
of the air and the soil. 

Man could live comfortably on what three plant families 
furnish, — the grasses, which include all the cereal foods 
and sugar; the pulse family, which furnishes most of our 
vegetable nitrogen; and the rose family, which includes the 
plants which furnish us our luxuries in the way of fruits. 
In eating animal products, man is still dependent upon the 
grass family to furnish food for the cattle from which he 
obtains meat, milk, cheese, and butter. For clothes, man 
depends indirectly upon plants for the leather and wool 
of the domestic animals, and directly for cotton and linen. 
Plants are the source* of many of the materials out of which 
houses are made and furnished. 

Some plants (bacteria) cause disease, while still others 
provide remedies with which to cure diseases. Plants 
please our eyes as we travel about. They keep up the 
supply of oxygen in the air; they rid the air of the carbon 
dioxide which we have cast off; they provide employment 
for millions of men who raise food plants, manufacture 
them into food, and distribute them throughout the world; 
and they employ other millions in the production of cotton 
plants and cotton cloth for our clothing. 

The farmer who raises plants has an interest in knowing 
what kind of soil and climate, how much water, air, and 
light each kind of plant needs to yield him the best results. 
To this end he has to know something about the habits of 
plants in general, and about their enemies and their dis¬ 
eases. He has learned by experience that some plants 
grow better when planted in hills; others in drills, and 
still Others sown broadcast. He is still trying to find the 
best kind of plant food for each plant, and the method of 


SCIENTIFIC INTEREST 


377 


cultivation which best enables plants to get their full supply 
of food and moisture, and he is-still fighting weeds which 
deprive the useful plants of their share of food, water, and 
light. Yet he is conscious, if he stops to consider, that he 
cannot make a plant grow. His part is to create good vital 
conditions. 

We are interested in the work of men who are trying 
by cross-pollination, grafting, and selection to reduce the 


Figure 349. —Tropical Vegetation. 
Note how different the plants are from ours. 



undesirable parts of plants and to increase their capacity for 
food, storage, or whatever we find desirable. Experiment 
stations maintained by the United States Department of 
Agriculture and by individual states are making many ex¬ 
periments in this field, especially in increasing the number of 
fruits on trees and in reducing the size of the seeds in berries. 

316. Scientific Interest. — In addition to practical in¬ 
terests, that is, besides the supreme importance of plants 








378 


PECULIARITIES OF PLANT LIFE 


to man and his dependence upon them, there is another 
interest, — that of the scientist in plants as organisms. 
The scientist studies how plants are like animals; how 
they differ from them; how each is dependent upon the 
other for waste products; how plants depend upon animals 
for the pollination of their flowers and the scattering of 
their seeds and how the plants make use of the wind and 
water for the same purposes. 

He studies, too, the increasing complexity of plants 
from the simple, one-celled plants dependent upon water 
for existence, up through the plants which are becoming 
accustomed to living on land, and finally to those which 
have complex systems and complex flowers. He finds that 
all are related, and the more he learns about them, the 
more interesting does he find their relationships. He is 
interested in seeing how the change from water to land calls 
forth changes in structure to fit the new environment; how 
in land plants, each one has adapted itself in form, size, 
arrangement of leaves, and so on, to make the best possible 
use of the air and water which it is able to procure. 

In trying to find the causes of such variations of plants the 
scientist performs many experiments, often upon the smallest 
plant, for size and complexity are no indication of the 
interest which may center in a plant structure. Bacteria, 
for instance, which are the simplest and smallest of all 
plants, are being studied more to-day than any of the others. 

Every year adds to our knowledge of the nature of plants, 
their relations to one another and to man. Besides these 
relations due to their surroundings, plants bear towards 
one another the relation of dependence and independence, 
which we have discussed under parasitism and symbiosis. 

Plant life itself remains a mystery. The poet Tennyson 
has given expression to thoughts of those who have tried in 
vain to solve the many problems which have arisen in con¬ 
nection with the study of plant life. 


REFERENCES 


379 


“Flower in the crannied wall, 

I pick you out of your crannies. 

I hold you here, root and all, in my hand, 

Little flower, but if I could understand 
What you are, root and all, and all in all, 

I should know what God and man is.” 

HOME WORK 

To show the response of stems to gravity, place seedlings or young 
plants in unnatural positions and note their effort to right themselves. 
To show the response to light, examine a potato from a dark cellar, which 
has sprouted in the spring; a plant that has been allowed to grow toward 
the light in a window; the bending of seedlings, and the like. For the 
storage of food, examine all the common garden vegetables and test them 
for the food which they contain. If possible, find some vegetables which 
have been kept for two seasons and have produced seed, and note their 
appearance after all the food has been used. 

Sprout slips of balsam, geranium, and ivy to get adventitious roots. 
Show such roots on the stem of a tomato plant where it has been allowed 
to lie on the ground, and on Wandering Jew. 

Examine leaves in the laboratory and in the fields to find illustrations 
of all the terms used. . Examine onions and cabbages for example of 
leaves modified for storage, and the onion also as an example of a re¬ 
duced stem. Find examples of all the terms used in the discussion of 
flowers and buds. Make collections of leaves of shade trees. 

QUESTIONS 

What are the ordinary adaptations of plants? What are the pe¬ 
culiarities of the plants that get their nitrogen from insects? Describe 
Indian pipe; mistletoe. Discuss the movements of plants. What 
are the commonest plant societies ? Mention the localities in which 
each is to be found. Name plants characteristic of each. Describe 
mistletoe and its effect on a tree. What is meant by plant succession? 
What is our economic interest in plants? What scientific interests 
have we? What are some of the facts we are trying to find out? 

REFERENCES 

Bergen and Caldwell, Practical Botany, pages 477-493. 

Bessey, College Botany, page 320. 

Plant Societies. 


CHAPTER XXIX 


SOME GENERAL PLANT PROBLEMS 

Students of botany had to make a study of plants before 
they could understand how to keep plants well, how to 
produce new kinds of plants, and how to solve similar prob¬ 
lems. It is more important to-day than ever before that 
such problems be solved simply because there are more human 
beings living to-day than at any previous time. In the pre¬ 
ceding chapters on parts of plants, you have been making a 
scientific study which has furnished you with reliable facts 
about the life of plants. This is the kind of study that all 
who know about the life of plants have made, and it should 
make it easier for you to understand the few general plant 
problems which have been merely outlined in this chapter, 
because whole books are needed for a complete discussion 
of them. 

317. Plant Diseases. — Three typical plant diseases', Cab¬ 
bage Yellows, Potato Wart, and Black Stem Rust, have been 
selected to illustrate how some of the fungi destroy our 
food plants. As you learn about each of these diseases, you 
will see that it is much more important that the disease be 
prevented than cured. Note the kind of knowledge neces¬ 
sary to recognize them and the methods used in treating 
them. In the case of the rust your attention is called to 
the complicated life history of this fungus parasite as it lives 
first on the wheat, then on the wild barberry in a never 
ending cycle. 

The farmer who would be successful must learn, how to 
recognize the common diseases of farm plants. If he does 
not know about this important part of farming, he can ask 

380 


PLANT DISEASES 381 

the Agricultural Experiment Station to tell him what he 
ought to know. 

Cabbage Yellows. — This disease is caused by a soil fungus, 
Fusarium conglutinans, which is not known outside of the 
United States. 

Effects. — The fungus attacks the roots of the plant either 
in the seed bed or soon after transplanting. It works 
greatest havoc during a hot, dry period, as warm soil favors 
its growth. The plants attacked soon become stunted 
and the foliage assumes a pale, lifeless, yellow color. The 
disease is often more severe on one side of the plant than the 
other, causing it to curve towards that side. The fungus 
enters through the roots and passes up to the stem and 
leaves through the vascular bundles which it soon clogs and 
destroys, as well as the tissue adjoining it. As the destruc¬ 
tion of the vascular bundles shuts off the plant’s supply of 
food-material and water, the lower leaves soon drop off 
through lack of sustenance, and the whole plant either 
becomes sickly and fails to head or dies outright, according 
to the severity of the attack. 

Destructiveness. — On fields moderately infected, from 50 
to 75 per cent of the crop is a loss, while in badly infected 
fields the crop is a total failure. 

How the Disease Is Spread. -— The fungus is carried from 
field to field in a variety of ways : for example, (1) by diseased 
plants from infected fields; (2) by water which drains from 
infected fields; (3) by wind blowing the dust from field 
to field ; (4) by vehicles, tools, and animals. 

Persistence. — Once introduced into the soil, it remains for 
long periods, experiments extending over fourteen years 
having shown it to be still present and active. Soil infested 
with this fungus is said to be “ cabbage sick,” but other crops 
grow well in it. 

Control Measures. —* Various measures have been tried 
as a means of eontrolling the disease: (a) Disinfection of 


382 


SOME GENERAL PLANT PROBLEMS 


seed and seed beds. These failed because the fungus was 
in the soil of the field and not on the seeds or in the seed 
beds. (6) Using new land for seed beds. This failed for 
the same reason, (c) Crop rotation, to give the fungus a 
chance to die out. A period of fourteen years was found to 
be too short, so that also was impracticable. ( d ) Fertiliza¬ 
tion of the soil with a view to obtaining such vigorous plants 
that they could resist the disease. No success was attained, 
(e) Soil disinfection, for the purpose of ridding the soil of the 
fungus. Nothing was found that was cheap enough or 
that would kill the fungus without being detrimental to the 
growth of the crop. (/) Finding plants able to resist the 
disease, based on the experience of finding now and then a 
head in a whole field that had been able to live when the 
rest were killed. 

The method used was to take such heads and raise seed 
from them for next year’s crop. These plants were found to 
produce a higher percentage of resistant plants, the best of 
which were then selected to produce the seeds for another 
crop. In this way strains have been developed that are 
practically immune to the attacks of the fungus. Much 
still remains to be done, but enough has been accomplished 
to make sure that success in combating the disease lies 
in producing disease-resisting plants. No one has yet dis¬ 
covered what the differences are that make immunity pos¬ 
sible in one plant and not in another. 

318. Potato Wart. — This is a disease dangerous to the 
common potato which has been known in Europe for many 
years, but which has been found in the United States only 
since 1918, when it was discovered in Pennsylvania. It was 
introduced on an importation of several millions of bushels 
in 1911, which were distributed over the eastern part of the 
United States. Much attention is now being given to 
locating centers of infection, in order that quarantines may 
be established. 


POTATO WART 


383 


Signs of the Disease. — The effects are found in the potato 
itself and not on the parts above ground, which accounts 
for its not being discovered till harvesting time. The first 
evidences of wart are small spongy outgrowths on the sur¬ 
face of the potato, especially at the eyes. Sometimes warts 
arise on different parts of the same potato, transforming 
it into a spongy mass 
which turns from brown, 
the first color, to black, 
and decays (Figure 350). 

What Causes Wart. — 

Wart is caused by a 
fungus which penetrates 
the outer coat of the po¬ 
tato and stimulates the 
cells to abnormal growth. 

When the wart decays, it 
fills the soil with millions 
of sporangia of two sorts, 
one capable of germinat¬ 
ing at once and infect¬ 
ing new potatoes or new 
places on the same po¬ 
tato, and the other rest¬ 
ing sporangia, capable of 
living over the winter and starting the infection anew in 
the spring, or lying dormant for years until conditions be¬ 
come favorable for germination. 

How the Fungus May Be Spread. — (1) By drainage from 
infected fields; (2) by distribution of the infected soil; 

(3) by the use of manure of animals which have eaten the 
raw potatoes; (4) by garbage into which peelings from 
diseased potatoes have been thrown; and (5) by planting 
diseased potatoes or those which have grown in infested 
soil and carry the spores on their surfaces. 



Figure 350 . — Potato Wart. 



384 


SOME GENERAL PLANT PROBLEMS 




Control of the Disease. — As the result of many experiments 
with disinfection, fertilizers, resistant varieties, and so forth, 

the best means of control seems to 
be to destroy or boil all potatoes 
grown on such infested land, to 
establish a strict quarantine to 
prevent its spread, and to practice 
rotation of crops over the period 
of eight years that the fungus is 
known to remain in the soil. It 
does not cause damage to any 
other cultivated crop, but it may 
propagate itself on other members 
of the potato family, especially 
such as grow wild. 

Courtesy of Experiment Station, 

University of Minnesota. JV 0^. AS an illustration Of the 

Figure 35^— Normal Grains application that may be made of 

biology, it may be said that the 
disease was first reported in this country by a biology 


University of Minnesota. 

Figure 352.—Grains of Wheat 
Affected by Black Rust. 


student in high school who had 
noticed potatoes in the field at 
home, but had not known the cause 
of the peculiar appearance or the 
seriousness of the disease till his 
teacher mentioned it in class. 

319. The Black Stem Rust of 
Grain and the Barberry. — The 
black stem rust of grain causes the 
loss of millions of bushels of grain 
every year. In 1916, a bad rust 
year, the loss in wheat alone in a 
single state, Minnesota, was about 
30,000,000 bushels. In 1917, not 
a bad rust year, the loss in the 
whole United States was about 14 





the black stem rust 


385 



per cent of the whole crop. The wheat affected by rust has 
shrivelled grains, which are light in weight, and straws which 
are crinkled and broken. 

The Cause of the Rust. 

— This is a fungus 
which lives as a parasite 
on the stalks and heads 
of grains and grasses 
during a part of its life 
history, and on the 
leaves of the common 
barberry for the other 
part. This is spoken of 
as the alternation of 
hosts, a habit which is 
characteristic of several 
other fungi which cause 
plant diseases (see page 
380). 

How It Spreads. — 

The fungus itself is 
composed of very small 
threads or hyphse which 
grow inside the leaves 
and stems of the host 
plant. It spreads from 
one wheat plant to an¬ 
other by means of spores 
which are carried by the 
wind, insects, or other 
means. In the early 
part of the summer these spores appear in red pustules on 
the stems and leaves of the infested plants, from which they 
fly like dust when the plants are disturbed. On account of 
their small size and large numbers, they fall on other plants, 


Courtesy of Experiment Station, University of Minnesota. 

Figure 353. — Diseased Heads of Wheat. 


386 


SOME GENERAL PLANT PROBLEMS 



some near at hand, and some long distances away. When 
moisture makes it possible, each spore sprouts and forms 

a new center of infection. These 
spores, called summer spores, are 
red or orange colored and egg- 
shaped. In the autumn another 
kind of spore is produced, namely, 
the black or winter spore. These 
appear in black pustules on the 
stems and leaves of the plants 
which serve them as host. These 
spores are longer, and have thick 
walls, an adaptation which en¬ 
ables them to live over the winter 
in stubble and straw. They are 
made up of two cells, and usually 
are not carried by the wind. 

When they germinate in the 
spring, each of the two* parts 
produces four round, colorless 
bodies called sporidia. These are 
blown about by the wind, but 
they are not able to propagate 
the disease unless they fall upon 
the barberry, where they produce 
a plant so different in appearance 
that it was for many years con¬ 
sidered a separate plant and given 
a different name. On the leaf or 
fruit of the common barberry, the 
sporidia produce yellow circular 
spots containing reddish spores in 
long chains. From the shape of the spot, this is often called 
the cluster cup stage. This stage is most active from May 
until midsummer. The spores from the plant on the barberry 


Figure 354. — Heads of Wheat 
Unaffected by Black Rust. 




THE BLACK STEM RUST 


387 


cannot reproduce on the barberry, but on being blown to 
the grains or certain grasses, they begin a new stage in the 
life history of the red rust. These propagate on the grain 
in the field as before. Another source of infection is the 


summer spores which may have lived over the winter on the 
grasses near the field, or 
on straw or stubble. A 
summary will put the his¬ 
tory clearly: (1) the red 
or summer spores spread 
the disease from wheat 
to wheat, or from wheat 
to grasses and back to 
wheat; (2) the winter 

spores formed on wheat 
or grasses in the autumn 
remain on them until 
spring when, by means of 
sporidia, the infection of 
the common barberry 
takes place ; (3) the clus¬ 
ter cups or spring spores 
on the barberry start the 
infection again on the 
wheat and grasses. 

Conditions Favoring the 
Rust. — Cool nights with 
heavy dews, followed by 
hot muggy days, afford ideal conditions for the growth of the 
disease. Any condition which favors the growth of the grain 
and retards that of the rust is unfavorable to the disease. 

Methods of Control. — No sure means has been found of 
curing the disease, but experiments have proved that there 
are several ways of reducing the amount of damage done by 
it. Among them may be mentioned clean cultivation, 



Figure 355. — Diagram of Life History 
of Red Rust of Wheat. 








388 


SOME GENERAL PLANT PROBLEMS 


which gets rid of the grasses on which it grows; planting 
early varieties of grain which mature before the rust has 
time to develop; planting varieties which have been found 
able to resist the disease ; and, best of all, getting rid of the 
common barberry. Denmark, which eradicated the bar¬ 
berry in 1903, has not had an epidemic of rust since. 

Note. — The Japanese barberry, more commonly planted 
for ornament than the common barberry, is immune to the 
rust, and may be spared. 

320. Plant Breeding. — Plant breeding is a general term for 
the various methods employed to improve a given variety 



Figure 356. — Variations in Yields of Good Seed Corn from Rows 
Planted with Seed from Two Different Ears. 


Crate on left, row 18, 19 pounds seed corn ; crate on right, row 11, 62 
pounds seed corn. Good seed corn worth three dollars per bushel in the ear. 
Only the ears from the high yielding rows are retained as seed corn for 
further experiments. 

of plants. It is well known that there is a wide range of 
variation (page 390) in plants as they grow in a field. In 
the case of food-plants, it is desirable to know the conditions 
which enable a plant to produce the most food. We are 
just beginning to understand some of the reasons why one 
plant is large and another small, why one plant gives a large 











METHODS OF BREEDING OATS 


389 


yield of seed and another a small yield. But it must be 
remembered that we are only at the beginning in our under¬ 
standing of some of these problems. The methods of breed¬ 
ing oats serves to illustrate why it is important that we know 
more about plant breeding and also illustrates the general 
problem. 

321. Methods of Breeding Oats. — The oat crop ranks third 
in New York State, having an annual value of about twenty 



Figure 357. — Types of Heads of Oats (see text). 


million dollars. The average yield per acre when the study of 
breeding oats was undertaken was about thirty bushels per 
acre whereas it should be not less than forty bushels per acre. 

The first step is to secure good seed which will produce 
large, healthy plants. Students of commercial oats recognize 




390 


SOME GENERAL PLANT PROBLEMS 


a dozen different types, and the first question to be settled 
is which shall be selected. This point is well shown in Figure 
357, which has two types of heads common in a field of oats. 
On the right is a branched head; on the left, the oat ker¬ 
nels are mostly on one side. Both these heads yield well, 
but the head that has the kernels on one side shows a greater 
tendency to lodge during a heavy wind or rainstorm, which 
makes this variety difficult to harvest. 

Before selection can be wisely undertaken, it is necessary 
to know the locality or environment in which the seed is to 
be sown and to learn which variety is best adapted to the 
locality. Some varieties are more resistant to drought than 
others, some are more susceptible to rust or more affected 
by smut, while others have stiffer straw, thicker hulls, or 
larger grain. 

Those who are making the experiments in plant breeding 
try to combine in one variety the best features of all, but it is 
difficult to produce just the results most desired. Many 
varieties of plants are improved regularly in nature by cross¬ 
pollination. In plant breeding man has taken advantage of 
this habit in plants and substituted pollen from a special 
variety when he sought to grow a plant with special features. 
But oats are regularly self-pollinated and when cross-pollina¬ 
tion is to be effected, the oat flower must be opened before it 
reaches the blooming stage and the three anthers must be 
removed. Then the flower is carefully closed and allowed to 
mature for two days before the pollen from the plant of the 
variety to be used is dusted on the pistil. 

The oat illustrates one of the difficulties which the plant 
breeder encounters. Each variety of plant has to be studied 
in just such a detailed fashion before any permanent improve¬ 
ment can be secured by plant breeding, which has become 
one of the most difficult and technical phases of plant study. 

322. Conservation. — Conservation is a term which was fre¬ 
quently heard during the war, in connection with sugar, coal, 


CONSERVATION 


391 


gasoline, and other articles of daily use. A broader use of 
the word includes our natural resources, such* as land, water, 
and mineral wealth, as well as the more personal ones. 

Conservation of land is being accomplished in three distinct 
ways, as follows: 

1. The Reclamation of Desert Land by Irrigation. — This 
is carried on in the western United States where the rainfall 



Figure 358. — Irrigating Ditch. 


is so scanty that only a few plants, especially adapted to 
extremely dry conditions (see page 371) can live. This 
region, although now a desert, lacks only water to make it 
productive. The water for irrigation is secured by building 
dams in suitable places and storing throughout the summer 
the water from spring freshets and melting snow on the 
mountain peaks. Closely connected with this phase of land 
conservation is dry farming , so called. This is possible as 
strains of wheat and other crops have been found which can 






392 


SOME GENERAL PLANT PROBLEMS 



grow with much less moisture than the ordinary strains 
demand. The use of such strains makes crops possible on 
land too dry for farming under ordinary conditions. 

The use of water for irrigation has been practiced from very 
early times especially in India and Egypt. The methods 
used there, and the results obtained, however, are insignifi¬ 
cant when compared with modern methods, a good example 
of which we find in the western United States. Immense 
dams are constructed which impound lakes covering many 


Figure 359. — Irrigating' Ditches. 

acres. The water from these lakes is let out, carried miles 
through canals and tunnels, and is distributed to crops 
as needed. In this way, nearly a million of acres have 
already been made fertile which before were unable to produce 
crops on account of the absence of rainfall. 

This work in the United States is carried on by the govern¬ 
ment under the name of reclamation 'projects. More than 
twenty such projects have been successfully carried out, 
and the land sold to settlers at reasonable rates. More 
than twenty thousand persons are now living in regions 
formerly unfit for habitation. It is estimated that there 




CONSERVATION 


393 


are about thirty millions of acres that can be reclaimed by 
carrying on this work. 

Any crop can be raised on irrigated land that the character 
of the soil and the climate make possible. All kinds of 
fruits are produced in abundance in some portions of the 
western irrigated lands, on others garden produce is raised, 
and on still others grains and hay. 

2. Reclamation by Draining. — This was formerly done 
only by private individuals and on a small scale. Within 
the last ten years, however, the United States Government 
has undertaken drainage projects on a large scale, especially 
in the Everglades of Florida.. The plan is to cut through 
the rim of land that hems in the swamps and form a chan¬ 
nel to the ocean for the water which now covers the land 
from a few inches to ten feet or more in depth. The main 
ditches will be large enough to serve also as canals for 
transportation, and for the distribution of water for irriga¬ 
tion in dry seasons. The work already undertaken will 
make available about 4,000,000 acres of land now Useless. 

In New York State, the building of the Barge Canal has 
made it possible to reclaim by drainage the large tract 
known as Montezuma Swamp at the foot of the finger lakes. 
Hundreds of acres now covered only with cat tails and other 
worthless plants will be suitable for truck farming, being 
fertile, level, and unusually free from stones. 

Swampy land near the ocean is often reclaimed by build¬ 
ing a loose retaining wall around it, and pumping in sand, 
mud, and gravel from the beach or from some other part of 
the swamp or marsh. Such land has little value for agri¬ 
cultural purposes, but it affords safe and convenient sites 
for buildings. 

As the population increases, and the demand for food 
grows stronger, more pains will be taken to make the best 
use of all land. Other countries are much in advance of 
ours in this respect. 


394 


SOME GENERAL PLANT PROBLEMS 



3. Rejuvenation of Worn-out Land. — In the eastern part 
of the United States there are many farms which have been 
abandoned because the soil has become so poor that there 
is no profit in the crops raised. This condition has come 
about gradually by taking crops off, year after year, without 

replacing food material 
for succeeding crops. 
Fertility can be restored 
by supplying proper ferti¬ 
lizers and by the rotation 
of crops some of which 
must be leguminous. (See 
page 257.) 

323. Conservation of 
Wild Flowers.—The main 
reason for the study of 
fungal diseases, plant 
breeding, and the general 
problem of conservation 
outlined in this chapter 
is their economic impor¬ 
tance to man. From time 
to time in the discussion 
of animals and plants in 
the previous pages of this 
book, your attention has 
been called to facts about 
living things without any 
thought of their direct eco¬ 
nomic bearing. In each 
instance we have been trying to give you a clearer under¬ 
standing of how animals and plants live, in the hope that 
some of this information will give you pleasure in the future. 

It would be a poor course in biology that did not emphasize 
the pleasure which knowing our wild flowers gives all lovers 


Figure 360. — Hepatica. 

One of the earliest wild flowers, and 
one of the greatest favorites. It should 
be left growing in its natural surround¬ 
ings, and not transplanted as a common 
practice is. Only a part of the blossoms 
should be picked from each bunch, in 
order that some may be left to mature 
and scatter seed. 




CONSERVATION OF WILD FLOWERS 


395 


of nature. We are coming to feel that animals and plants 
which give pleasure to us should be permitted to live. Game 
laws and animal preserves are helping to protect some of 
our rare animals that were being destroyed by man. The 
time has come when simi¬ 
lar provisions should be 
made for our choice and 



rare plants. 

Owing to the limited 
area of wild tracts, par¬ 
ticularly near cities, wild 
flowers will soon disap¬ 
pear utterly unless the 
public is educated to en¬ 
joy them as they grow. 

The study of plants which 
you have just made tells 
you about their habits so 
that you may know how 
to deal with them. For in¬ 
stance, little harm is done 
by picking the flowers of 
trillium, because its 
thickened stem, deep in Figure 361. — Fringed Gentian. 
the ground, will put up One of the flowers that is eagerly sought 
another flower stalk the after by flower pickers as a result of which 
. it is becoming less and less common. As 

next year, if it has tood j s an ann ual, picking all the flowers 
enough stored to enable prevents its further growth in that region, 
it to do SO. In the case This flower should not be picked by friends 
. . of wild flowers, 

of arbutus, however, it is 

difficult to pick the blossoms without pulling loose from 
the soil the long trailing stem, which is then left to die. 
In your study of the flower, you have learned that the 
seeds are developed in the flower and if you pick all the 
flowers, no seeds can be formed. Lovers of wild flowers 





396 


SOME GENERAL PLANT PROBLEMS 



Figure 362 . — Pink Lady-slippers. 


One of the disappearing orchids. In many places incessant picking has 
exterminated it. It is doomed to extermination unless the boys and girls 
start a crusade to save it from the older men and women who are old- 
fashioned in their way of appreciating wild flowers. Orchids are perennials 
but they need their leaves to store up food for next year’s blossoms and seeds. 
Naturally they fruit every year, and the older plants are surrounded by little 
groups of seedlings, which is nature’s way of stocking the woods with these 
delightful flowers. Every one that is picked and brought in tends to make 
the woodland barren and so much less attractive. Spare the wild flowers! 

are coming more and more to enjoy leaving them where 
they grow instead of picking them for decorating their 
homes, where they last for only a few hours at best. 

Photographing wild flowers where they are found growing 
is a form of recreation that is becoming popular. 






HOME WORK 


397 


SUMMARY 

No one can be a successful agriculturist or a successful 
forester without having a knowledge of what plants are, 
how they grow, what conditions suit each kind of plant best, 
how to till the soil to secure those conditions as nearly as 
possible, what the relations are among the plants themselves 
and what the relations of other organisms are to plants, 
especially to cultivated plants. This makes necessary a 
wide study of insects, the worst enemies of plants, and of 
birds, the enemies of insects, also a study of bacteria and of 
fungi, which cause large losses to the farmer in attacking 
the crops he is raising. Until we realize how complex these 
relations are and how much depends on knowing them, we 
shall, as a nation, never make the best use of the resources 
we have. The study of biology ought to help boys and girls 
to think about these things, and to make applications of 
them in their everyday life. 

QUESTIONS 

What is the use of studying plants scientifically ? Name the plant 
diseases discussed. Tell how each is caused. What is the remedy for 
each? What is plant breeding? What are the objects of plant breed¬ 
ing ? What is conservation ? In what ways is land being conserved ? 
Why should wild flowers be conserved? How can this be accom¬ 
plished ? 

HOME WORK 

Make a list of the plant diseases you know. Try to find out what 
causes each and how it injures the plant. Make a list of the remedies 
you know of for each disease, such as sprays. Find out from the 
owner of a farm how many bushels of each crop his land produced to 
the acre. Compare this with the average for the United States. Ac¬ 
count for the difference. What can be done to improve a low yield? 
Make a list of the wild flowers that grow in your locality. Inquire 
from some older person what flowers formerly grew there in abundance. 
What can you do to help save those that remain? If you own a 
camera, try making photographs of wild flowers growing in their nat¬ 
ural surroundings. 


/ 


398 SOME GENERAL PLANT PROBLEMS 

REFERENCES 
National Geographic Magazine. 

Bulletins of the United States Department of Agriculture. 
Bulletins of the Experiment Stations of your state. 

Bergen and Davis, Principles of Botany, pages 500-513. 
Gager, Fundamentals of Botany, pages 520-570. 



PART III 


HUMAN BIOLOGY 

CHAPTER XXX 

RESEMBLANCES BETWEEN MAN AND THE OTHER 
ANIMALS 

324. Man as an Animal. — In our study of animals and 
plants, the life processes have been emphasized. We have 
found that each living thing can be analyzed according to the 
place where it lives and its food habits ; its structures used in 
securing life-giving oxygen and removing wastes; its organs 
for responding to light, heat, cold, sound, etc.; and finally 
its methods of producing more living things like itself. We 
also found in plants an additional life process, the ability 
to manufacture their own food from the uncombined and 
non-nutritious elements in the air and soil. As we approach 
the study of man, we naturally ask how all these facts that 
we have learned about animals and plants help us to under¬ 
stand how man lives. 

One of the best ways to learn about man is to study his 
life processes just as we did the grasshopper’s and the frog’s. 
In such a study we may omit the comparison with plants 
except incidentally, because man is an animal in all the 
points in which our comparison is to be made, and the simi¬ 
larities between animals and plants have already been em¬ 
phasized on pages 4-8. This does not imply that man is 
nothing more than an animal, but simply that in many 
features of his life he lives as animals live. 

399 


400 


MAN AND THE OTHER ANIMALS 


Some of the men who have made a special study of the 
fossil remains of man in the rocks believe that man began 
living in Europe about 25,000 years ago. This is their esti¬ 
mate of the length of time that has passed since the rocks 
were formed in which are found jaw bones or the bones of 
the legs and arms. In all such cases so far there has been 
no difficulty in recognizing these fossil bones as belonging 
to man, although the races of people who lived fifteen or 
twenty thousand years ago no longer exist. 

The earliest homes of man must have been the shelter of 
trees and an occasional cave, and it is in certain caves in 
Spain and France that many early records of man are to be 
found. There is no record of when man first began to use 
fire or to build definite shelters. In fact, both these neces¬ 
sities in our cold climate were not as important to early 
man, because he appears to have wandered about in tropical 
and sub-tropical regions. This was even true of the climate 
of Spain and France in the period when he lived in the caves 
which have become famous for their many records of the 
early life of man. With the coming of the glacial period, the 
climate of all northern Europe and northern America 
became much colder and the men who lived in regions that 
were influenced by the southward movement of the ice 
sheets had to adopt some means of keeping warm or perish. 

But as soon as the number of men became so great that 
they needed to go farther for the necessary food, we may 
suppose that protective measures were gradually used. 
Moreover, the same forces that compelled early man to 
migrate have continued to impel man to move out into un¬ 
known parts to see if he can find an easier place to live. We 
shall see how this has come to have a vital influence upon 
our own lives as we examine more fully into man’s life 
processes. 

We have lived in houses heated in winter so long that we 
had begun to feel that it would be impossible to get along 


MAN, AS AN ANIMAL 


401 


without a furnace fire; but we have all read how whole 
sections of France during the war had no heat and that our 
American soldiers were able to adjust themselves to what 
seemed to most of us an almost impossible change. This 
teaches us two important lessons: first, it shows something 
of how early man may have lived; and secondly, the wide 
range of adaptation in the body of modern, civilized man. 
This second lesson is very important because it encourages 
us to undertake physical difficulties which we had thought 
impossible; because we now realize that we can overcome 
them after having the heroic examples of the men, women, 
and children of Belgium and France. 

It is also easier now than ever before to realize how man 
can live in all parts of the earth. When we described 
where frogs, fish, and grasshoppers were to be found, certain 
limits had to be made. Not so with man. He possesses 
something that no animal has — the power to rise above the 
limitations of his surroundings. This he does by building 
a house of ice in the northlands and spreading a tent of cloth 
in Arabia. His constructive ability has led man to invent 
various devices for his protection such as stone, brick, wood, 
or iron houses, something that no animals are able to do in a 
manner that justifies their being compared with man in this 
respect. It is true that birds build nests, but they are always 
built in the same fashion; and it is true that beavers build 
dams, but they are always made of wood. The reason that 
man is able to do more different things than animals is 
because he has a better mind, a mind that can adapt itself 
to many different kinds of work, such as that done by car¬ 
penters, engineers, lawyers, teachers, etc. 

Name some others. Tell what you can about the range of 
adaptation in animals that have not been domesticated by 
man. These simple and well-known comparisons give us 
some indication of the sense in which man and animals are 
similar and it is in this sense that we wish to work out the 


402 


MAN AND THE OTHER ANIMALS 


comparison of the life processes of man with those of 
animals. 

Scientists give four reasons in explaining why certain ani¬ 
mals and plants are not adapted to living in all parts of the 
world : (1) lack of suitable food ; (2) failure in adapting their 
lives to the peculiarities of climate; (3) too many enemies; 
(4) inability to raise their young. All these man has been 
able to overcome. 

STUDENT REPORT 


The following table points out some of the common adaptations 
in animals. How are they related to the animal’s success in life? 
Name some other habits which help to protect animals. 



| Active in Summer 

Active in Winter 

Home 

Protection 

Earth 

Water 

Air 

Nest 

Night Feeding 

Day Feeding 

Color 

External Skeleton 

Method of Escape 

Earthworm .... 

Fly. 

House Sparrow . . . 

Dog. 

Man. 

Etc. 













325. Youth, Maturity, Old Age. — The life of man is 
divided into three general periods, which are youth, the 
period of maturity, and the period of old age. These same 
terms are given when describing the life of animals and plants. 

Youth is the period when living protoplasm always grows, 
if furnished with proper food. This is the time when boys 
and girls grow taller and heavier each year; when the tree 
grows new leaves and the limbs become longer; and when 









































QUESTIONS 


403 


the small puppy is turning into a full grown dog. During 
this period of change the boys and girls, the tree, and the 
puppy are all nourished by food and this makes it possible 
for them to grow. 

Maturity is the period when man ceases to grow taller, 
although he continues to eat food as he did during the period 
of youth. The living protoplasm in his body does not in¬ 
crease in amount. The same can be said of the tree, for 
it does not grow taller; and the puppy of last year has 
become a full grown dog. During this period of maturity, 
each living organism is able to repair its body as fast as the 
body wears out. The period of maturity varies with differ¬ 
ent things ; in some butterflies lasting but twenty-four hours, 
in man continuing for about twenty-five years. 

Old age in man begins when the body wastes faster than it 
is repaired, and in the tree when growth is over and decay 
begins. During this period of old age all living things use 
food as they did in youth and maturity, but it cannot build 
up the body as fast as it is worn out and death is the final 
result. Old age occurs at different ages in different individ¬ 
uals ; and the same is true of animals and plants. 

SUMMARY 

Man has the same life processes as the animals. He is able 
to live in all climates and localities on the earth. No plant 
or animal can do this. Civilized man has learned to control 
his surroundings. Animals and plants are controlled by their 
surroundings. Man like all other living things passes through 
periods of growth, known as youth, maturity, and old age. 

QUESTIONS 

What have you learned about plants and animals that will help you 
to understand how man lives? Where are the earliest records of man 
found? Why do men migrate? Why can man control his environ¬ 
ment? How do you understand the terms youth, maturity, and old 
age? 


CHAPTER XXXI 


DIGESTIVE ORGANS AND FOOD 


sopha^us 


326. Digestive Organs. — The digestive organs of man 
consist of the same parts which have already been described 
in the frog. Each region of the 
digestive organs is more perfectly 
developed and the biological princi¬ 
ple, the division of labor, reaches 
its highest development in man. 
The parts of the alimentary canal 
in man are: the mouth, containing 
the teeth, tongue, and glands ; the 
throat or pharynx; the esophagus, 
the stomach, the small and the 
large intestine. The last part of 
the large intestine is called the 
rectum. These several parts form 
a continuous tube, and each does 
a particular work in digestion 
(Figures 363 and 72). 

The mouth is lined with a soft 
kept moist by the 
saliva secreted by three pairs of 
glands, and poured into the mouth 
The spleen is not a digestive in sufficient quantities to moisten 
gland. The salivary glands con- the dry food and thus assist in 
shown swallowing. The tongue is a mus¬ 

cular organ and bears on its upper 
surface many small fleshy projections called papillce (pa- 
pil'le: Latin papilla, bud), some of which are fairly large 

404 



Figure 363. — Alimentary 
Canal of Man, with Its Two 
Chief Digestive Glands, the membrane 
Liver and Pancreas Con¬ 
nected with the Small In¬ 
testine. 





DIGESTIVE ORGANS 


405 


and are arranged on the back of the tongue in the form of 
a V (Figure 364). 


Our power to taste sweet, sour, bitter, and salt, which 
are the four fundamental tastes in man, is due mainly 


to certain nerve cells located 
on the larger papillae. The 
food stimuli received by the 
special sensory cells of the 
papillae are carried to the brain 


Figure 364 . — Tongue of Man 
Showing Two of the Three 
Kinds of Papilla. 

The circumvallate papillae 
are at base of tongue and about 
five or six in number; the 
fungiform papillae are numer¬ 
ous, round, mushroom-like pro¬ 
jections scattered over the 
surface of the tongue. The 
third type of papillae, the fili¬ 
form, are the most numerous 
and like coarse hairs. You can 
recognize these papillae on your 
own tongue. 



Figure 365 . — Diagram of Taste 
Cells in the Tongue. 


The taste cells are much longer 
than the surrounding cells. The 
nerve which carries taste stimuli 
to the brain ends among these 
long cells. 



by the taste nerves. In the brain the food stimulus is 
interpreted as sweet, sour, or bitter (Figure 365). 


LABORATORY STUDY 

Blindfold in turn several members of the class and have each hold his 
nose while a small amount of some highly flavored food is placed on the 
tongue. Such common foods as maple sirup, vanilla extract, mar¬ 
malade, jams, etc., are admirable for this test. Make a record of each 



406 


DIGESTIVE ORGANS AND FOOD 


test. This experiment will prove that we do not taste flavors. Remove 
the hand from the nose and again taste the same substances. This 
time there will be no difficulty in telling the name of the substance 
because it has been smelled as well as tasted. 


The roof of the mouth is called the palate. The front 

part contains supporting plates of bone and is therefore 

called the hard palate. The back part (the soft palate) is a 

thin sheet of muscle covered by the 

mucous (mu'kus) lining of the mouth. 

The soft palate separates the mouth 

from the nasal cavity. Beyond the 

soft palate is the throat cavity called 

the pharynx. This is a funnel-shaped 

cavity, having two openings at its 

lower end, the front one being the 

opening into the windpipe which leads 

to the lungs, and the rear one, the 

opening into the esophagus. In the 
Figure 366. — X-ray of , £ ,, , . 

Three Teeth. upper part oi the pharynx, on each 



side, is the opening of a Eustachian 
(u-sta'ki-an) tube which passes to 
the middle ear. 

Teeth. — Just back of the lips are 
the teeth. In adults there are thirty- 
two, sixteen in each jaw, belonging 
to four classes according to shape. 
In front are the eight incisors (in- 
sl'zers) with sharp cutting edges; next the four sharp-pointed 
canines (ka/nins), and back of the canines the eight pre¬ 
molars (pre-mo'lers) shaped for tearing and crushing, while 
the remainder of the teeth, twelve in number, are the flat- 
topped molars which do most of the grinding of the food. 

Care of the Teeth. — We all know that the teeth are hard. 


Note how firmly the 
bone fits around the roots. 
These teeth are in good 
condition. The white 
blotches on the molar tooth 
are the places where this 
tooth has been filled. This 
is the new way of examin¬ 
ing the teeth. 


That, however, does not prevent them from becoming broken 
by carelessness or accident, or from decaying because of 


DIGESTIVE ORGANS 


407 


neglect. When the teeth are not cleaned, a substance called 
tartar forms on them, which prevents the bacteria from being 
rubbed off and sometimes pushes 
the gums away from the teeth. 

The bacteria cause food particles 
to ferment and form acids which 
dissolve the hard outside covering 
(enamel) and then rapidly the 
softer parts of the teeth. This 
results in toothache, a foul breath, 
and the imperfect chewing of 
the food. The teeth should be 
brushed after each meal to re¬ 
move particles of food, particularly 
sugar which ferments easily. At 
least once a year there should be 
a visit to the dentist who will re¬ 
move those portions of teeth that 
are decayed and fill cavities, thus F ' IGURE Vertical Section 

preventing further decay. 

The teeth of children often come in on the outer or inner 

side of the jaw instead of 
on the middle. This re¬ 
sults in an irregular row of 
teeth. Such teeth do not 
meet the opposite teeth as 
they should (Figure 369). 
Dentists know how to 
straighten such teeth and 
produce better results, if 
they can begin their cor¬ 
rective treatment before 
the teeth are fully grown. This is very important not only 
for one's looks but especially for one’s health as without such 
treatment proper mastication is often impossible. 



Figure 368. — Milk Teeth. 

Age 3| to 4 years. Notice the perma¬ 
nent teeth deeper in the jaws. 











408 


DIGESTIVE ORGANS AND FOOD 


The esophagus is a nearly straight tube connecting the 
mouth with the stomach. It passes through the diaphragm 
(Figure 395), enlarges, and becomes the stomach. As 
soon as one swallows, control of the food is lost, and further 
action becomes involuntary. Two sets of muscles, one ex¬ 
tending lengthwise, the other around the esophagus, act 

together in forcing the food 
or water into the stomach. 
This explains why we can 
drink from a brook when 
the head is much lower 
than the stomach. 

Stomach. — In man the 
stomach is the largest sec¬ 
tion of the digestive tube, 
and it has a capacity of 
about three pints. It is usually described as pear-shaped 
although there is much variation in its form (Figures 370 
and 371). At the point where the esophagus joins the 
stomach there is a muscular ring (< cardiac valve, kar'di-ak) 
which ordinarily prevents, the food from passing again into 
the esophagus. In vomiting, this valve be¬ 
comes relaxed. The opening at the larger 
and lower end of the stomach is guarded 
by a similar valve {pyloric, pi-lor'ik) which 
serves to retain the food in the stomach Figure 370 .— Pear- 
until certain digestive changes have taken shaped Human 
place. Stomach - 

The intestine has two parts, a small, much coiled tube 
about an inch in diameter and about twenty feet long called 
the small intestine, and a large section about five feet long 
and four inches in diameter, bent in a rough f| shape and 
called the large intestine. At the junction between these two 
regions projects a short sac, the vermiform appendix (ver'- 
mi-form ap-pen'diks). The disease called appendicitis 




Figure 369 . — Permanent Teeth. 



DIGESTIVE ORGANS 


409 


(ap-pend-i-sl'tis) affects this organ. The 
large intestine ends in a special region 
called the rectum. The opening of the 
rectum to the outside is the anus (a/nus). 

The esophagus, stomach, and intestine 
are each lined with a membrane that is 
similar to that found in the mouth cavity. 

This membrane is called the mucous 
membrane. In the esophagus, the mucous 
membrane is smooth and moist thus fur¬ 
nishing an easy passage for the food; in 
the stomach this membrane is in folds 
except when the stomach is full of food; 
and in the intestine, it has a velvet ap¬ 
pearance due to projections called villi 
(Figure 374). The numerous glands of 
the stomach and intestine are located 
in the mucous membrane. 

Glands. — A gland is a group of special cells which secrete a 
fluid. The glands which produce 
the digestive fluids are (1) the three 
pairs of salivary (sal'i-va-ry) glands, 
located below the ear, and beneath 
the tongue and lower jaw; (2) the 
numerous gastric (gas'trik) glands 
found in the lining of the stomach, 
possibly 5,000,000 in number (Fig¬ 
ure 373); (3) the pancreas; (4) the 
liver, the largest gland in the body; 
and (5) numerous intestinal glands 
in the small intestine. 

STUDENT REPORT 

Fill out the following table and de- 
The constrictions are natural, scribe the digestive system of the animals 



Figure 372. — X-ray Photo¬ 
graph of Large Intestine 
of Man Showing Appendix. 



Figure 371. — X-ray 
Photograph of 
Human Stomach. 


This is a shape 
familiar to physi¬ 
cians and is just as 
normal as the shape 
shown in Figure 370. 





410 


DIGESTIVE ORGANS AND FOOD 


studied in Part I. This will help you to understand better the parts of 
the digestive system of man and the work that each part does. 



One Cell 

Many 

Cells 

No 

Digestive 

Tube 

Digestive 

Tube 

No Well- 
defined 
Digestive 
Glands 

Which 

Ones 

Requike 

Food? 

Paramecium 
Hydra . . 

Earthworm 
Frog . . . 

Man . . . 

Etc. . . . 








327. Food. — One of the best definitions of food is the 
following. Food is that which when taken into the body 
builds up tissue or yields energy. All organic foods or food¬ 
stuffs are divided into three classes, the proteins (pro'te-ms),. 
the carbohydrates (kar-bo-hl'drats), and the/ate. This classi¬ 
fication is made whether we study the foods of a plant, an 
animal, or of man. Scientists are able to- tell to which class 
meat, bread, oatmeal, milk, and all other foods belong by 
finding out the chemical composition of each. The chemists 
have made a thorough study of food and tell us that certain 
chemicals are present in each of the three classes of foods. 

Definite chemical tests tell us to which of these three classes 
any given article of food belongs. In general it may be 
said that the proteins are necessary for the growth and the 
repair of the body, and that the carbohydrates and fats 
furnish heat to keep the body warm, and energy for muscular 
work. The unused fat is stored up as fatty tissue. All 
classes of food are found in the various foods obtained from 
plants. Some, like honey, are nearly pure carbohydrate, 
while the English walnut contains, in addition to fat, a large 
quantity of plant protein. Animal foods can furnish us with 
only proteins and fats. In primitive times man used a re¬ 
stricted diet and led an active out-of-door life. To-day 
















DIGESTION 


411 


man is living on a mixed and varied diet. This is to be 
regarded as an acquired habit and one that is questionable 
when carried to an extreme. The question of how much 
to eat is a modern problem, and on its solution depend our 
health, length of life, and energy for work. 

STUDENT REPORT 

Animals eat a large variety of things, parts of which serve to furnish 
energy or to nourish the body. In the following report, work out the 
sources from which the animals derive their food. To what extent are 
they alike? 



Para¬ 

mecium 

Hydra 

Earth¬ 

worm 

Frog 

Man 

Flies 

Minute plants . . 

Minute animals . 
Plants .... 

Flies. 

Add food of man . 








328. Digestion. — Digestion begins in the mouth. The 
teeth break up the food and mix it with the fluid of the 
mouth, the saliva which contains the enzyme, ptyalin. Dur¬ 
ing this process, sugars and starches are changed into soluble 
sugars. The fluids of the mouth are usually slightly alkaline 
(al'ka-lm or lln, a chemical term, the opposite to sour or acid), 
but as soon as the food passes into the stomach it enters an 
acid (sour) medium, and the digestive action of the saliva is 
destroyed in a short time by the stomach fluid. For this 
reason, the sugar and starch undergo no further digestive 
changes until they reach the intestines. 

Into this acid medium of the stomach, the gastric glands 
(Figure 373) pour out the gastric juice (a digestive fluid), 
and the enzyme pepsin in this juice acts on the proteins so 
that they can later pass through the walls of the intestines. 
In the stomach the heat of the body dissolves some of the 

















412 


DIGESTIVE ORGANS AND FOOD 


fats into oils, but many of the fats used as food remain solid 
at body temperature and are unchanged in the stomach. 

After one or two hours the food passes into the intestine 
and undergoes further changes in another alkaline medium. 

Here the pancreatic juice, which is made in 
the pancreas, comes into contact with the 
digested and partly digested food, causing 
three different changes. One is to complete 
the change of proteins into simpler products; 
a second is to finish converting starches into 
sugar; while the third is to assist the bile 
(the digestive juice made in the liver) to 
digest the fats. The digestion of the food 
is practically completed in these three re¬ 
gions of the digestive tube, although diges¬ 
tion continues to some extent after the food 
is passed into the large intestine. 

The pepsin in the gastric juice is called an 
enzyme (en'zlm : Greek enzymos, fermented) 
or ferment. There are three different en- 
of the inner wall of zymes in the pancreatic juice (trypsin, 
the stomach pro- amylopsin, and steapsin), none in the bile, 
ject into the tissiies anc j one j n ^ sa p va These enzymes are 
of the stomach as . . J 

minute pockets, the chemical bodies which digest food. All 

The cells shaded plants and animals digest their food by 
in this drawing are meang of enzymes . 
the ones that are ~ 

at the end of the Inorganic foods, such as water, oxygen, 
pocket and are the and salts, man takes into his body, making 

tKegastric jutee*' 6 them , part of his living P roto P la sm, or using 
them in oxidation. There is a large amount 

of water in man, enough to make up nearly two thirds the 
total weight of his body. All of his food contains water. 

Oxygen is breathed in from the air, and the various salts, 
such as common salt, sodium chloride (so'di-um klo'rid, or 
rid), calcium (kal'si-um), magnesium (mag-ne'zhi-um, or 



man Gastric 
Gland. 

The linine cells 




ABSORPTION OF FOOD 


413 


-shi-), 'potassium (po-tas'si-um), and phosphorus (fos'for-us) 
are taken in with our food. They are useful to the body. 
A small amount of iron is also contained in food and water 
and becomes a part of the red blood cells. 


STUDENT REPORT 
Where the Food Is Digested 



In the 
Cell 

In the 
Leap 

Primitive 

Digestive 

Tube 

Stomach 

Mouth 

Digested 

by 

. Enzymes 

Paramecium . 
Hydra . . . 

Frog .... 
Man, etc. . . 

Bean .... 
Yeast .... 








LABORATORY STUDY 

Study food and food tests. Artificial gastric juice is easily prepared 
by taking \ gram of pepsin, cc. of strong hydrochloric (hi-dro-klo'- 
rik) acid and adding 50 cc. of water. Take white of egg that has been 
cooked and subject it, in a test tube, to the above mixture. A variety of 
tests should be made, with and without heat (100° F.), with and without 
the acid. Pancreatic juice is made by uniting 15 grams sodium (so'- 
dl-hm) carbonate (kar'bbn-at), 5 grams pancreatin (p&n'kre-a-tin), and 
100 cc. water. The action of this fluid may be tested as above on the 
fats, as olive oil; on starch, as flour; and on proteins, as raw lean meat 
or milk. Also examine several of the common articles of food to deter¬ 
mine to what class of foodstuffs they belong. 

329. Absorption of Food. — The absorption of food in man 
and animals is the process of taking the digested foods 
from the alimentary canal into the blood. Practically no 
food is absorbed in the mouth or esophagus, and but little 
in the stomach. 

The absorption of food from the intestinal canal is done 
by small folds in the lining of the small intestine. To the 
















414 


DIGESTIVE ORGANS AND FOOD 


naked eye, these folds appear as a covering of minute hairs, 
called villi (vil'li). Their structure is shown in Figure 374. 

The process of osmosis, which has been so frequently 
referred to in Part I, is the chief factor in the passing of 
the food into the blood vessels. This process is assisted by 
the action of the living cells in a manner not well understood. 

The digested proteins and sugars pass directly into blood 
vessels which lead to the liver. In the liver, these blood 

vessels unite to form the portal 
(por'tal) vein, which is divided 
into minute branches that dis¬ 
tribute the blood to the cells 
of the liver. As the blood thus 
passes among the liver cells, 
the larger part of the sugar is 
changed into glycogen (gll'ko- 
jen), an animal starch, and 
stored temporarily in the liver 
cells. This stored-up starch, 
glycogen, does not yield energy 
to the body. It is given out 
gradually from the liver and 
changed back into sugar in 
which form it does yield energy 
to the body and results in 
keeping a uniform amount of 
sugar in the blood. 

The fats pass into certain distinct vessels, lacteals (lak'- 
te-als), which in turn open into larger ones. Eventually 
these vessels unite to form a large duct — the thoracic — 
which empties into one of the veins near the heart. The 
food is now in the blood stream and is carried to the individ¬ 
ual cells of the body. Each cell takes the kind of food which 
it needs and by a series of changes, as yet only partly known, 
makes the food into living protoplasm. 



Figure 374. — Diagram of a Villus 
from the Inner Wall of the 
Intestine. 











ABSORPTION OF FOOD 


415 


The indigestible part of the food is not absorbed, but 
continues to move through the small intestine into the 
large intestine, and on through the rectum. During this 
progress much moisture is absorbed, especially in the large 
intestine, which leaves the “ undissolved food ” harder 
and harder. The regular removal of the unused part of 
the food, fceces (fe'sez), is of much importance in main¬ 
taining health, because the bacteria living in the digestive 
tract cause the waste material to decay and the poisonous 
substances thus formed are injurious when absorbed into 
the blood. 

Foods normally remain in the stomach from one to five 
hours, and in the small intestine about four hours; while 
they may be from six to twenty-four hours in passing through 
the large intestine. 

We become hungry each day and feel relieved only after 
eating. A person frequently eats a large meal because of 
an extra amount of work that is to follow. But is he helped 
to do the extra work? Probably not, for the strength to 
do the work of to-day comes from the food eaten yesterday, 
or possibly the day before yesterday. The food, even after 
digestion is completed, must pass through many changes 
before it is built up into protoplasm. The actual building 
of the food into protoplasm is the process for which the word 
nourishment is used, and it should not be confused with 
absorption. 


Food as 
purchased 
contains 


' Edible portion f Water. 

e.g., flesh of meat, yolk and I 
white of eggs, wheat, flour, j 
• etc. [ Nutrients' 

Refuse 

l e.g., bones, entrails, shells, brain, etc. I 


Protein. 

Fats. 

Carbohydrates. 
Mineral matter. 
Vitamines 
(vi'ta-mlnz). 


Alcohol is made up of carbon, hydrogen, and oxygen. 
All proteins contain nitrogen in addition to these three. 





416 


DIGESTIVE ORGANS AND FOOD 


Because alcohol contains no nitrogen, it cannot be used as 
a food to build up tissue. 


USES OF NUTRIENTS IN THE BODY 


Protein Forms tissue 

e.g., white (albumen) of eggs, 
curd, casein (ka'se-In) of milk, lean 
meat, gluten of wheat, etc. 

Fats Are stored as fat 

e.g., fat of meat, butter, olive 
oil, oils of corn and wheat, etc. 


Carbohydrates 
e.g., sugar, starch, etc. 

Mineral matter (ash) 
e.g., phosphates of lime, 
potash, soda, etc. 

Vitamines found in 
milk, eggs, meat, fruit, 
vegetables, and whole grains 


Are transformed into fat 


All serve as 
fuel to yield 
energy in the 
form of heat 
and muscular 
power. 


Shares in forming bone, 
assists in digestion, etc. 

Help keep people 
well and promote the 
growth of children. 


Heat is a form of energy and one of the reasons for taking 
food is to keep up the supply of this energy. The more work 
a person does the more energy he uses, but even a resting 
body uses some energy, for the heart beats and the muscles 
of the chest move. The amount of this form of energy a 
person uses is measured by a unit of heat named the calorie 
(kal'b-ri). A calorie represents the amount of heat required 
to raise the temperature of a pint of water about four 
degrees Fahrenheit. A man in rising from a chair, walking 
eight feet, and returning to the chair uses about one calorie 
of energy. 

The term calorie just defined is now used throughout the 
civilized world as the common unit of measurement for food 
energy. Through the studies of experts it has been deter¬ 
mined how many calories are necessary to keep the human 
body from starvation, how many more must be added if 
the body is to do light physical work, and how many more 
if heavy manual labor is done. By knowing the total number 




DAIRY -COWS 

NUMBER ON FARMS AND RANGES. 
APRIL 15. 1910 


417 


ABSORPTION OF FOOD 



• Figure 375 . 

Which states furnish the most milk, butter, and cheese ? Which the least ? 




























418 


DIGESTIVE ORGANS AND FOOD 


of people in a city and the average amount of work done, it 
is possible to estimate how much food must be sent to this 
city to keep the people alive and to enable them to do their 
work. The adoption of the calorie unit thus serves to intro¬ 
duce accuracy into all calculation of food uses. 

What the daily calorie needs are : 

For a workingman 3500 to 4000 
For an active woman 2800 to 3000 
For a sedentary man 2200 to 2800 
For a sedentary woman 1800 to 2300 
Youth 14 to 16 years 1500 to 3200 
Active soldier 4000 

One must keep in mind that our bodies require energy to 
grow new cells and to keep the old ones in repair; to keep the 
body at a constant temperature winter and summer; and 
to furnish energy for muscular activity, which often requires 
more energy than to carry on growth and maintain a constant 
temperature. To meet these needs of every human being 
a variety of foods is needed. 

In the classification of foods given on page 13 into proteins, 
carbohydrates, fats, mineral matter, and vitamines, the 
arrangement is made upon their chemical composition be¬ 
cause foods do not grow as proteins or fats. The foods that 
we eat are often composed of all these. There are five food 
groups which are arranged chiefly on the proportionate 
amounts of proteins, sugars, or fats. These are shown in the 
table on the following page. 

A well-balanced diet contains a proper proportion of these 
five food groups. One food from each of these groups should 
be used each day. It is impossible to prescribe an exact 
diet for every one, as it should vary with the age, weight, 
health, occupation, and location of the individual. The 
variation, however, is largely in the quantity rather than in 
the kind used. 


SOURCE OF FOOD 


419 


Food Groups 


No. 1. — Fruits and 


Purposes 


Amount Needed Daily by 
a Man at Moderate 
Muscular Work 


vegetables. 

No. 2. — Medium-fat 
meats, eggs, cheese, 
dried legumes and 
similar foods, milk. 

No. 3. — Wheat, corn, 
oats, rye, rice, and 
other cereals, pota¬ 
toes, sweet potatoes. 

No. 4. — Sugar,honey, 
sirup, and other 
foods consisting 
chiefly of sugar. 

No. 5. — Butter, oil, 
and other foods con¬ 
sisting chiefly of fat. 


To give bulk and to 
insure mineral and 
bod y-r egulating 
materials. 

To insure enough pro¬ 
tein. 


To supply starch, a 
cheap fuel, and to 
supplement the pro¬ 
tein from Group 2. 

! To supply sugar, a 
quickly absorbed 
fuel, useful also for 
flavor. 

To insure fat, a fuel, 
which also adds to 
the richness of food. 


1| to 3 pounds. 


8 to 16 ounces (4 
ounces of milk 
counting as 1 
ounce). 

8 to 16 ounces (in¬ 
creasing as foods 
from Group 2 de¬ 
crease) . 

1 } to 3 ounces. 


\\ to 3 ounces. 


330. Source of Food. — The food necessary to the life of 
man must all be grown — must have all been alive at one 
time. In this respect man is exactly like all plants and ani¬ 
mals. Before the miller can prepare the flour, the wheat grain 
must be planted, grow into a mature plant, and produce more 
wheat grain. There is no short cut in the growing of wheat, 
nor has any man a patent on the process. Man can neither 
lengthen nor shorten the general growth period necessary. 
The same is true of all food groups. Meat and eggs pass 
through a growth period that is just as definite and regular 
for them as are the periods of growth for wheat or corn. In 
the final analysis man has to wait until nature has produced 
the various food groups before he can utilize them. 

Intimately associated with the ultimate production of our 













420 


DIGESTIVE ORGANS AND FOOD 


foods are many biological problems of great importance. 
Several of these have been mentioned from time to time in 
the sections devoted to zoology and botany. Numerous 
insects feed upon our growing crops, and as the acreage 
increases, more food is furnished for these same insects, 
until the damage done by them amounts to millions of 



Figure 376. — A Typical Western Wheat Field. 


The ripe grain is being cut by a self-binding reaper. The bundles of 
wheat are set up into shocks or stooks of about twelve bundles each. 
Here they must remain until the grain dries, which takes about one week in 
good weather, after which it can be threshed. Photograph furnished by 
the Omaha Chamber of Commerce. 

dollars annually. It requires all of man’s skill to prevent 
them from destroying some crops. 

Not only are animals destructive to the grains and fruits 
but many fungous diseases attack these same groups of 
plants and kill them or prevent them from producing a good 
yield. Again, all animals must have their food manufactured 
for them in just the same sense that man does; so that man 




FOOD SUBSTITUTES 


421 


and animals are both dependent upon the green plants. 
There is thus a never ending interrelationship between 
animals and plants that requires the utmost skill of man to 
adjust, if human beings are to have enough food to eat, 
especially as our cities increase in size. 

331. Food Substitutes. — Foods that can be used in place 
of those that we wish to save are known as food substitutes. 



Figure 377. — A Grain Elevator. 


Here wheat and other cereals are stored before sending them to the mill 
to be ground into flour or manufactured into breakfast foods. Photograph 
furnished by the Omaha Chamber of Commerce. 

For example, the substitutes for wheat are corn, oats, rice, 
barley, white and sweet potatoes; while the following can 
be used in place of meat: fish and other sea food, milk, cheese, 
eggs, nuts, legumes, and cereals. Honey, maple sirup, corn 
sirup, sorghum, and molasses are used in place of sugar; 
the substitutes for butter and lard are olive oil, corn oil, 
cottonseed oil, meat drippings, etc. 

A great deal is being said about new foods in the study of 
















422 


DIGESTIVE ORGANS AND FOOD 


food substitutes, but there are really no new foods. The use 
of rye flour, corn meal, and such foods, while new to many 
people of this generation, were the most common foods with 
our ancestors as they pioneered and settled the land. We 
are in reality returning to the simpler forms of food rather 
than adding new foods. Find out all that you can about the 



Figure 378. — Flouring-mill where Wheat is Turned into Flour. 


One of these large mills in Minneapolis has the equipment to turn out 
sixteen thousand barrels of flour every twenty-four hours. Photograph 
furnished by the Omaha Chamber of Commerce. 

different kinds of foods that were used by the early settlers 
in your community. 

332. Food Shortage. — Keeping in mind the important fact 
that all foods have to be grown, it is easy to understand how 
there may be a food shortage. If the men who are skilled in 
raising food were all removed from the farms, the store¬ 
houses would in a short time be emptied of their supplies, 
and none would be growing to replace them. This would 







INCREASING THE FOOD SUPPLY 423 

result in a food shortage. With the growth of cities, more 
food has to be collected and transported for the use of their 
populations, none of whom are engaged in the production of 
food, but all of whom require food. 

Some appreciation of the magnitude of this phase of our 
food problem can be gained by learning from your local 
dealers where the food used for one day in your home was 
grown. Apples and peaches are often so abundant in certain 
parts of New York state that large numbers of bushels are 
never even picked some years because the cpst of labor and 
transportation is greater than the price that can be realized 
for the fruit when it is sent to market. The problem of 
giving all the people in our country enough to eat at reason¬ 
able prices is one of very great importance and one that 
you can well afford to study. 

333. Increasing the Food Supply. — Whenever an in¬ 
creased demand is made upon the total supply of food in a 
nation, as was made upon the United States during the years 
of 1916-1919, attention is directed to two important facts: 
(1) that we are not using all the available foods as is noted 
by a study of food substitutes; and (2) that measures must 
be employed to increase the total production of food. To 
show that biological principles are the foundation for all 
such studies, three examples only will be given. 

1. Fish Production . — The first food chosen to take the 
place of meat is fish because the food value of fish is similar 
to that of meat. “ In America we have hardly begun to 
utilize our fish supply. There are said to be available 
nearly 70 kinds of salt-water fish and more than 30 fresh¬ 
water varieties, yet the average person knows not more than 
a dozen. How many different kinds of fish have you ever 
eaten f It is said that every year the fishermen of the Atlantic 
coast throw away about 10,000,000 pounds of fish that have 
a higher nutritive value than New England's famous cod. 
We are far behind other countries in our use of fish. Against 


424 


DIGESTIVE ORGANS AND FOOD 


our 18 pounds per person each year, England used 65 pounds 
and Canada 57 pounds.” 

We should not only eat more fish but study the conditions 
under which fish live in order that fish may become more 
abundant in our fresh-water streams and lakes. Fish freshly 
caught is one of the food delicacies. Many of our fresh¬ 
water lakes and ponds could be made to supply an abundance 
of fish food if some intelligent care were taken to supply 
these ponds with the varieties best adapted to live in them. 

Perch, pike, bass, and bullheads have a wide range of adap¬ 
tation and will thrive in most of our fresh-water ponds. We 
have not as yet begun to utilize properly the larger streams 
of our country which can be made to support a great number 
of food-fish if the water in them is reasonably pure. Where 
the streams are utilized to carry away the sewage of cities 
and towns, the water becomes so polluted that fish cannot 
live in it. 

2. Improving the Varieties of Animals and Plants. — If one 
compares the domesticated animals and plants in common 
use 20 years ago with those of to-day, many improvements 
are easily noted. These are due to a large number of experi¬ 
ments that have been carried on largely by the United States 
Department of Agriculture and the many state experiment 
stations. Here new varieties are tested and old varieties 
improved for the benefit of man. The net result of all these 
experiments has been to increase greatly the usefulness of 
our many domesticated animals and plants. The up-to-date 
farmer is thoroughly familiar with the latest discoveries 
in this field and often pays high prices for improved seed 
in order that he may obtain a larger yield. By keeping in 
touch with such improvements, the farmers have greatly 
increased the total food supply. 

3. War Gardens. — This is a garden in a back lot or other 
hithertofwaste land that is being used for the purpose of 
increasing food production. In addition to the large number 


INCREASING THE FOOD SUPPLY 


425 



of adults that were cultivating war gardens during the years 
of 1917-1918, there were approximately one million and a 
half school children enlisted in the United States School 
Garden Army during the summer of 1918. It is believed 
that an average of one fifteenth of an acre per pupil is a 
conservative estimate. This would make a total of one 
hundred thousand acres. The average production per acre 
under intensive cultivation at a low estimate ought to be $50, 


Figure 379. —War Garden. 

which would give a total of fifty million dollars in value 
(Figure 379). Experienced truck gardeners expect to make 
from $1000 to $1200 per acre. How much did you make? 

In addition to increasing the general food supply, there are 
two other reasons why the War Garden idea should be per¬ 
petuated. In the first place, the vacant lots of a city or town 
present a more attractive appearance when under cultivation 
than when occupied by weeds and rubbish. Secondly, they 
furnish a splendid opportunity for boys and girls to learn how 
many of their food plants grow and the meaning of labor. 








426 


DIGESTIVE ORGANS AND FOOD 


What other ways can you suggest that will help to increase 
the general food supply? 

334. Public Markets. — These are the places where those 
who raise garden truck, chickens, and other food products can 
bring them and the people can buy directly without paying 
the middleman or the retailer for his services. There is the 
further advantage that such foods are usually fresh. It is 
necessary to regulate the public markets in order that the 
food shall be properly prepared, and correctly weighed or 
measured. These markets are of great advantage to the 
poor people in cities, as they can get more good food at less 
cost than anywhere else. Is the market in your city well 
regulated? What are the rules governing it? 

335. The Preparation of Foods. — Some foods, such as 
milk, fruit, and nuts, may be eaten without being cooked, 
but most of our food has to undergo this process before it 
is suitable for eating. As no two kinds of vegetables Or 
meats are best cooked in exactly the same way, attention 
should be given to the preparation of food for the table. 
Successful cooking accomplishes three ends. (1) Changes 
are brought about to make the food more digestible, such 
as softening or dissolving it. (2) The nutritious parts are 
carefully saved. (3) The food is made attractive in appear¬ 
ance and taste, “ good to eat.” 

Every woman who wishes to have a happy, healthy 
family should make a serious study of cooking. Many of 
the facts about the nutritive elements which foods contain, 
and the many changes which they undergo in cooking are 
found out by chemists who study them in laboratories. 
It is not necessary for us all to know all these facts, but 
a good cook follows the rules and recipes which have been 
made as a result of scientific laboratory studies. 

To illustrate how much is involved in cooking, let us 
see what it means to produce a loaf of wholesome bread. 
Flour contains much starch, some sugar, some mineral 


THE PREPARATION OF FOODS 


427 


substances known as phosphates, a large quantity of gluten 
(a protein), and some bacteria (tiny plants, see Chapter XXIII) 
which may or may not be of value in making bread. When 
water is added to the flour, it becomes tough and sticky, 
this being a characteristic of gluten, and the most important 
one, so far as the making of bread is concerned. A small bit 
of yeast (a small plant, see Chapter XXIV) is added to the 
water used in making bread, and the dough is placed where it 
will be neither too hot nor too cold (70°-80° F.). 

The yeast begins to grow rapidly, feeding on the proteins 
of the flour, and as the yeast grows, it acts on the sugar. 
A substance called zymase (zim'as), an enzyme secreted by 
the yeast plant, breaks the sugar up into carbon dioxide, 
alcohol, and a small quantity of glycerin. The gas tries to 
escape, but is held in by the sticky dough. If the yeast plant 
is well distributed, the gas collects in many small bubbles, 
and the loaf is fine-grained. The alcohol keeps other plants 
from growing there, and also helps to soften the gluten. 

When the loaf is put into the oven, the heat kills the 
yeast plant, drives off the carbon dioxide, and causes the 
alcohol to evaporate. The heat changes the gluten into 
a substance more easily digested and of a more pleasant 
taste. In “ salt rising ” bread, bacteria from the air, instead 
of yeast cells, form the gas which makes the bread light. 
When a batch of bread “ sours,” it is usually because harmful 
bacteria get into the dough and grow more rapidly than the 
yeast plants. Sometimes other kinds of yeasts than the 
helpful ones employed in bread-making accidentally get into 
the batch of bread and it spoils as a result. 

During the war we used substitutes in our wheat flour 
with the result that many good cooks were not able to make 
as good bread as usual. This was not the fault of the cooks 
but was due to the following facts. Although corn, barley, 
and wheat flour contain nearly equal amounts of similar 
proteins, the proteins of corn, barley, and rye do not react 


428 


DIGESTIVE ORGANS AND FOOD 


the same to' water and the acids produced during fermenta¬ 
tion. The dough made from these substitute flours does not 
hold together and is not so distensible as that made from 
wheat flour. These unfavorable conditions of the dough 
can be improved by adding a small amount of what is known 
as the “ proteins of serum/’ a special preparation that is 
in the form of a dry powder. 

336. Adulteration of Foods. — Foods are adulterated either 
by subtracting some of the nutritious parts and substituting 
less valuable parts, or by adding materials which cannot 
act as a food. 

The food formerly subject to the most adulteration was 
milk. This adulteration was accomplished by adding water 
to make the milk go farther when being measured out, and 
adding formalin (for'ma-lin) to make it keep sweet. 

For a time many of the cereals were adulterated with 
sawdust, peanut shucks, or bran. Many of the special 
foods put up in packages used to be adulterated, and it 
would require a long description to enumerate all that have 
been found unsatisfactory for food by the Department of 
Agriculture. 

337. Pure Food Laws. — The Food and Drugs Act passed 
by the United States Congress on June 30, 1906, requires of 
manufacturers of foods and drugs that a definite statement 
be made as to their composition. A number of regulations 
and rules have been issued from time to time. The last 
was issued June 15, 1917, and related to the marking of 
the quantity of food in packages. Here we find that when 
food is in package form, it must be plainly marked in terms 
of weight, measure, or numerical count on the outside of the 
package. The quantity of the contents so marked shall 
be the amount of food in the package. 

This Pure Food and Drugs Act established high standards 
for many of the common and necessary foods of man. Before 
its adoption there was no standard for the manufacturers 


INDIGESTION 


429 


to go by. One of the reasons why it has been so valuable 
is because it includes so many different products. Food 
standards have been established for the following: meats, 
meat extracts, milk, cream, butter, cheese, ice cream, grains, 
meals, flour, fruits, vegetables, flavoring extracts, of which 
there are twenty-four, tea, coffee, cocoa, vinegar, and salt. 

The wide range of patent medicines and drugs comes under 
the influence of this act and we can now read their composi¬ 
tion on the label. This is a great protection against mis¬ 
branding and cheating. 

338. Indigestion. — Few children that have an oppor¬ 
tunity to romp and play out-of-doors and have plenty of 
simple and plain food ever experience any ill feeling in 
the digestive canal. However, as children grow older, 
exercise less, and eat richer food, they may suffer much 
inconvenience from indigestion. 

Indigestion is a condition which rarely extends to all 
parts of the digestive canal; it is located either in the stomach 
or in the small intestine. This may indicate that certain 
kinds of food are not properly digested. Indigestion may 
be caused by eating the wrong kinds of foods or by over¬ 
loading the stomach. If the food is chewed thoroughly, 
the appetite is usually a safe guide as to the amount needed 
by the body. Moreover, food thoroughly chewed is more 
easily acted upon by the digestive fluids. 

To some people certain foods are indigestible at all times, 
while other foods are indigestible only at special times. 
We should learn to understand our bodies in this particular. 
Some of the causes of indigestion are: lack of sufficient 
regular exercise, too much rich food, and the failure to drink 
enough water. 

Students and professional men use their brains more 
than their muscles, but they require protein to repair nerve 
waste just as laborers require proteins to feed their tired 
muscles. Unless students and professional men exercise 


430 


DIGESTIVE ORGANS AND FOOD 


their muscles, they do not feel vigorous and eager for their 
work. On the other hand, unless the laboring men exercise 
their brains, they do not do their work as well as they might . 
The proper amount of exercise varies with the individual. 
The best way to prevent indigestion is to have regular habits 
of eating and exercising. 

There are in the market many tablets and remedies for 
indigestion, which may, for example, contain pepsin and 
pancreatin. Now we know that these substances when 
found in the pancreatic fluid act in an alkaline medium. 
As these tablets must first pass into the stomach, which is 
an acid medium, the action of the pancreatin is probably 
destroyed long before the remedy reaches the intestine 
where it would naturally act. This means that such tablets 
are largely useless and it is one of the reasons why many 
doctors believe that digestive tablets are doing more to cause 
indigestion than they do to help it. There are only a few 
commercial tablets made which act on the undigested foods 
of the intestine. No medicine, in fact, can give permanent 
relief to indigestion. Predigested foods, an attempt to 
relieve indigestion, serve a useful purpose in cases of sickness, 
but in our regular life, should be used sparingly because they 
do not give the digestive organs the proper amount of work 
to do. 

339. Effect of Alcohol on Digestion. — Alcohol taken into 
the digestive tube is closely related to the question of in¬ 
digestion. The lining (mucous membrane) of the stomach 
and intestine is delicate and tender, and it contains thou¬ 
sands of cells which secrete the gastric juice, and many more 
thousands that help to digest the food. When alcohol comes 
in contact with these delicate cells, it prevents them from 
doing their normal work. The result is that food is not 
properly digested. 

Indigestion Disguised by Alcohol but Not Cured. — It is a 
serious error to regard alcohol as a genuine remedy for 


QUESTIONS 


431 


indigestion or abdominal pain. It is true the sense of pain 
is sometimes abolished by alcohol, and as a result of this 
many a man believes that alcohol aids his digestion, whereas 
it merely exerts a numbing effect on the stomach nerves, and 
his indigestion is disguised rather than removed. In fact, 
instead of being cured the mischief is increased since diges¬ 
tion is retarded. Some digestive medicines contain enough 
alcohol to be injurious. Alcoholic drinks taken with meals 
make the food hard to digest because the alcohol makes the 
food tough. 

SUMMARY 

Man has a definite set of digestive organs that are more 
highly developed than those of any other animal. These 
digestive organs prepare proteins, carbohydrates, and fats 
so that they pass into the blood. The blood is forced by 
the heart through definite blood vessels. The study of food 
is important because we require food in order to live. The 
cost of food and the amount needed are problems that 
science is helping to solve. 

QUESTIONS 

What do man and other animals require in order to grow? Name 
the kinds of foods. What is the value of protein? Of carbohydrates? 
What is a calorie? What are food substitutes? Name several ways 
in which the supply of food can be increased. What does cooking do to 
foods? Why is this important? What is digestion? What is indiges¬ 
tion? Absorption? How are the cells of the body fed? 


CHAPTER XXXII 


MOVEMENT 

In the introduction to biology and man, we have seen how 
man came to live in all parts of the world in well made houses 
to protect him from the cold and rain. In this respect he is 
superior although similar to all other animals. As we studied 

his use of food, there was 
seen also to be a funda¬ 
mental similarity between 
man and animals. Now 
as we take up the next life 
process of movement the 
same relationship will ap¬ 
pear. 

We usually think of man 
as walking or running, and 
it is only when we witness 
an acrobatic performance 
that the wide range of 
movements possible in man 
is realized. That man can 
do so many more things 
with his body than any 
other animal is due to the 
greater development of his nervous system. The structures 
by means of which he moves and which are described in 
this chapter are the muscles and the skeleton. 

340. Skeleton and Muscles. — Muscles which serve to 
move the body cover and protect the skeleton of man. The 

432 



Figure 380. — Skeleton. 






THE SKELETON 


433 




Figure 381 . — Cartilage. 

Note that the living cells are separated 
by spaces represented by small dots. 


more delicate organs of the 
body are protected further 
— the heart and lungs by 
the ribs, and the brain by 
the cranium. The skeleton 
and muscles of man are 
similar to the correspond¬ 
ing parts in the frog and 
the dog. Certain technical 
differences are noted by 
anatomists, but in general 
plan or structure and in 
their functions, the skeleton 
and muscles are alike in all 
the higher animals. 

341. The Skeleton. — Unlike the rest of the body the 
skeleton proper is hard. It consists of bone and a compara¬ 
tively soft substance known as carti¬ 
lage, or gristle. There are cells in 
the bones just as there are cells in 
the liver, the muscles, and in the 
nervous system. So, like the other 
parts of the body, the bones grow 
because the individual cells are sup¬ 
plied with food from the blood. 

Cartilage occurs near the ends of 
the bones, in the ear, and in the nose. 
It is especially prominent in the wrists 
and ankles of children. Therefore 
children should not be lifted by their 
hands or allowed to stand until a 
certain amount of bone has taken the 
place of this soft cartilage. This is 
readily appreciated when one examines an X-ray of the wrist 
of a child, which is almost entirely composed of soft cartilage 


Figure 382 . — Diagram to 
Show the Structure of 
Bone. 

The large circle, H, is a 
branch of the Haversian 
canal where the blood ves¬ 
sels are found. The spaces 
between the lines and oval 
black masses is bone. 









434 


MOVEMENT 


while the adult wrist has well-formed bones. The transition 
from soft cartilage to hard bone is due to the formation of 
mineral matter that takes the place of the cartilage. 

The erect position of man gives to his skeleton important 
characteristics which the skeletons of other animals do 
not possess. Among these may be mentioned the curves 



Figure 383 . — X-ray of 
Hand of Child. 


The bones in the wrist 
are forming. Between the 
joints of the fingers are 
seen small bones that later 
unite with the bones of the 
hand. Compare with Fig¬ 
ure 384. 



Figure 384 . — X-ray of Hand 
of Adult. 

What changes have taken place 
since childhood ? 


in the spinal column, the large hip bones, and the heel and 
arch of the foot. 

342. Joints. — The numerous bones in the skeleton allow 
the body to move although giving a certain amount of rigidity 
and permanence of shape. Wherever two bones meet and 
allow movement, the term joint or, more technically, articula¬ 
tion, is applicable. The joints are divided into three classes : 
(1) Immovable joints (sutures), found in the skull of the 





BROKEN BONES 


435 




Figure 386 . —X-ray of Broken. 
Femur. 


adult. The bones of the skull do not become firmly united 
until the head has reached full size, after which no movement 
- takes place be¬ 
tween these 
bones; (2)mov¬ 
able joints, such 
as the ball-and- 
socket joint in 
the shoulder 
and hip and the 
hinge joint in 
the elbow, 
wrist, knee, and 
ankle; (3) the 
mixed joints of 
the spinal col¬ 
umn which al- 
low only a 
limited move¬ 
ment. 

-— The movable 

joints are bound 
closely together 
by strong bands 
of connective tissue. These bands 
are called ligaments. The tear¬ 
ing or stretching of these liga¬ 
ments is called a sprain. 

343. Broken Bones. — When 
the bones of a limb are broken, 
the physician sets them, i.e. places Figure 387 .— X-ray of the Same 
the broken ends together, and Bone AFTER Healing. 
puts splints on the limb to keep th « lar S e “ oa > lus ” of 

^ ^ newly formed bone which makes 

the parts from slipping until the this bone stronger than before it 
new bone has formed (grown) and was broken. 


Figure 385 . —X-ray 
of Dislocated 
Finger. 







436 


MOVEMENT 


hardened. In Figure 386 is shown an X-ray photograph of 
a recently broken femur. In Figure 387 the same bone is 
shown. A large “ callus ” of new bone has formed around 
the broken ends, which gradually hardens, making this part 
of the bone stronger than ever. 

344. Structure of Bone. — One of the long bones from the 
arm or leg illustrates best the several parts. There is the long 
shaft with knobs on each end. These enlargements are the 
heads of the bone. The outer surface is covered with a 
tough membrane. If such a bone is sawed lengthwise, the 
following additional parts can be recognized: the long 
central cavity of the shaft filled with marrow; the hard bone 
of the shaft; the spongy bone toward each end; and the 
thin layer of cartilage covering each head. 

LABORATORY STUDY 

Study the skeleton, and examine long, flat, and irregular bones. 
How is the bone modified to do its work ? 


STUDENT REPORT 

Make a report on the skeletal structures of a nim als as follows: 
External 



Absent 

Jointed 

Not 

Jointed 

Horny 

Bony 

Internal 

Paramecium . 
Crayfish . . . 

Clam .... 
Frog .... 
Man, etc. . . 










345. Muscles. — The muscles are the lean parts of the 
flesh of animals. They are covered by the skin and are usu¬ 
ally dark in color. Birds are an exception, for their breast 
meat is generally white. Muscles are of two kinds : volun¬ 
tary (governed by the will), such as those which we use in 














IMPORTANCE OF THE MUSCLES 


437 


walking, or in moving the arms, Figure 388; involuntary , 
such as those which move the food along the digestive tract 
or assist in breathing. 

The voluntary muscles consist of many long muscle cells 
(fibers) bound together by connective tissue into a distinct 
bundle. Usually the muscle bundle 
is attached at each end to the bones 
through the tendon of connective 
tissue. A single muscle moves the 
arm in one direction only, and in order 
to lift the arm from the desk to the 
head, for instance, several muscles 
must act together. 

The cells of the involuntary mjiscles 
are unlike the cells of the voluntary 
muscles. Involuntary muscle cells oc- 
. cur in layers in the walls of the diges¬ 
tive tube, blood vessels, the bladder, 
and the like, and they are not under 
the control of the will. 

The muscular tissue of the heart has 
characteristics of both the voluntary 
and involuntary muscles, so that it 
may almost be said to belong to a 
special class. 

346. Importance of the Muscles.— 

When we remember that 40 per cent 
of the weight of the human body is in r inTundlesThich 
the muscles alone and that one fourth is an adaptation that en- 
of the blood is found in these same ables the le & t0 be movbd 

.... J . .in various directions. 

muscles, their importance is appreci¬ 
ated. But this great mass of tissue so richly supplied with 
blood is solely for the purpose of producing movement. In 
addition to the movements that we are accustomed to see, 
such as the motion of the arms, legs, and the head, there is 










438 


MOVEMENT 


the continued beating of the heart, the rhythmical contrac¬ 
tions of the stomach and intestines, as well as movement in 
other organs. To all these should be added the wide range 
of movements in facial expressions. To accomplish these 
varied motions man uses more than five 
hundred muscles. 

347. Action of a Voluntary Muscle. —• 

By placing the hand on the front of the 
forearm and raising the hand toward the 
shoulder, the muscle under the hand be¬ 
comes shorter, thicker, and firmer. At 
the lower end of this muscle, a strong 
cord can be felt as the forearm is lowered. 
This cor^l is the tendon that attaches the 
muscle to one of the bones of the forearm. 
The upper end of the muscle is covered 
by other muscles, but we know that it is 
attached to the shoulder blade by two tendons. This muscle 
is the biceps, and like all other arm and leg muscles consists 
of a central part, the belly. It has its origin on the shoulder 
blade by two tendons and is inserted on the radius bone 
by one tendon. When a voluntary muscle produces motion, 
the two ends of the muscle are drawn closer together and 
the belly becomes shorter, 
thicker, and firmer. The 
living muscle cells are the 
only parts that undergo 
any change in shape, while Figure 390 . — Involuntary Muscle 
the living cells in the con¬ 
nective tissue sheaths and in the tendons remain unchanged. 

348. Nerve and Blood Supply of Muscles. —The muscles 
are richly supplied with numerous large and minute blood 
vessels and it is the blood that gives the deep red color to 
muscles. In recent years scientists have discovered that 
each muscle fiber is supplied with a fine branch of the main 




Figure 389 . — Vol¬ 


untary Muscle 
Cells. 

Showing how the 
cells are bound to¬ 
gether with connec¬ 
tive tissue. At the 
end of the muscle, 
the cells of the con¬ 
nective tissue form 
the tendon. 









RECOVERY FROM FATIGUE OF MUSCLES 439 


nerve that enters the muscle. This important fact enables 
us to understand how the nervous system is able to control 
the actions of our muscles. 

349. Food of Muscles. — The blood flowing through the 

muscles carries food to the muscle cells. The most important 
of the food substances used in the contraction of a muscle is 
grape sugar, or glucose. This sugar is formed in the body in 
digestion from starch and cane sugar. Glycogen, the stored- 
up sugar in the liver, is also used to furnish energy in con¬ 
traction, but not until it has been transformed into sugar. 
A small amount of fat is present in muscles and may be 
used up during their contrac¬ 
tion. Under ordinary circum¬ 
stances the protein foods do not 
furnish energy for contraction, 
but are used to repair the actual 
wastes that take place in the Figure 391. — Heart Muscle 
muscle cells as they do work. Cells. 

350. Fatigue of Muscles. — After you have played hard for 
a time, you become tired and want to rest. You are tired or, 
to express it more scientifically, your muscles are fatigued. 
When you are taking your physical exercises, some of the 
movements make your arms ache, and you do not do them in 
good form. You are using muscles that do not get much 
exercise and they become quickly fatigued. You may con¬ 
tinue to move your arm until it is impossible to move it any 
longer. In such cases of extreme fatigue not only are the 
muscles tired but also the nerve cells. Two things are in¬ 
volved in the fatigue process of a muscle: first, there is the 
using up of the food energy necessary for muscular contrac¬ 
tion ; and secondly, there is the accumulation of waste sub¬ 
stances produced by the activity of the muscles. 

351. Recovery from Fatigue of Muscles. — It is difficult 
to separate entirely a consideration of the muscles from the 
nervous system, as already explained, but some facts indicate 






440 


MOVEMENT 


in part what probably happens in the muscles as they are 
again made fit to do work. If the exhausted soldier is given 
a small amount of sugar while on the march, his fatigue is 
lessened. This is because sugar is quickly absorbed and 
is used by the muscles as a source of energy for contrac¬ 
tion. This indicates that food will restore muscles. A 
second factor in relieving fatigue is rest, which gives the 
muscle cells time to recuperate by gradually building up the 
muscle protoplasm, and removing wastes. As the energy 
required for the action of a muscle is mainly in the 
muscle protoplasm, there are changes that take place in it. 
Not all the energy can be used in the contraction of the 
muscle, and what remains is a waste substance that has to be 
removed. The removal of this waste is a large factor in re¬ 
lieving fatigue in muscles. 

352. Physical Training. — We are now in possession of the 
facts that enable us to understand the reason for physical train¬ 
ing and some of the benefits to be derived from it. It is true 
that walking and running are forms of exercise, but they are 
both limited to but a part of the more than 500 muscles of 
our body. Every morning our soldiers and sailors are put 
through the “ setting-up ” exercises. These are similar to 
those that you have in school each day except that there 
are more of them. These exercises aim to give every muscle 
in the body a chance to do its proper work. People unaccus¬ 
tomed to a full set of setting-up exercises find themselves lame 
and sore after the first few times. This is because they ex¬ 
erted muscles that had been unused for a long time and these 
muscles are not so strong as they ought to be. In a short 
time this lameness disappears and the morning exercises 
then give vigor and zest to the body. 

These exercises thus serve to keep the bulk of our body, 
our muscles, in a healthy state. Such a condition has an 
important bearing upon our ability to do good work with 
our brains because the mind works best when the rest of the 


QUESTIONS 


441 


body feels fit and full of energy. The physical examination 
of the drafted men in the United States during 1917-1918 
indicates that we have not paid enough attention to keeping 
our bodies in physical condition and when the opportunity 
came for many to render one of the greatest services that one 
can for his country, they were found to be physically unfit. 
What man can take pride in being physically unfit to serve 
his country? It is our duty to take our physical exercises 
seriously in order that we make our bodies as strong and 
vigorous as possible. 

SUMMARY 

Man is able to move about as other animals. This he does 
by means of his muscles and skeleton, under the direction 
of the nervous system. The skeleton is covered by muscles 
and skin. Bones grow and are fed just like muscles or any 
other tissue in the body. The bones of the skeleton move by 
means of joints which are held in place by ligaments. Bones 
grow new bone, as is seen in the broken femur. There is a 
definite plan of structure to all bones. The muscles are the 
flesh covered by the skin. The muscles are both voluntary 
and involuntary. ' Muscles are important both in the total 
weight of the body and in the numerous movements that they 
produce. Each muscle causes movement through the action 
of its individual cells, which are supplied by nerves and 
blood vessels. The muscle protoplasm is supplied with food 
for contraction purposes and food to repair the wastes. 
Muscles become fatigued and require food, rest, and the re¬ 
moval of wastes in order to recover from this fatigue. Physi¬ 
cal training is valuable in helping to develop properly all 
the muscles of the body, in keeping the body well, and in 
making it the best body possible. 

QUESTIONS 

How does the skeleton of man compare with that of the crayfish ? 
How do bones grow? Why do they grow? Where is there the most 


442 


MOVEMENT 


cartilage in our skeletons? What are joints? What is a sprain? 
How do broken bones heal? How does muscle differ from bone? 
How many kinds of muscles are there? What is the work of each? 
Why are muscles important? What is the relation of the nervous 
system to muscles? What is the importance of the blood vessels to 
the muscles? Explain how the different foods are used by muscles. 
What is the value of physical training? 


/ 


CHAPTER XXXIII 


RESPIRATION AND EXCRETION 



In this chapter are combined the two fundamental life 
processes of respiration and excretion together with a descrip¬ 
tion of the more important organs 
that are necessary to the per¬ 
formance of these processes. Two 
important practical problems are 
suggested as a result of a discus¬ 
sion of these topics. The problem 
of leather naturally follows the 
description of the skin and the 
problem of sewage follows the 
general subject of excretion. 

353. Respiration is the life pro¬ 
cess in which oxygen is used in 
the cells of 
the bodies of 
plants and 

animals, and carbon dioxide eliminated 
from them. All animals carry on respira¬ 
tion, and in all the process is alike, al¬ 
though the various animals use different 
structures to secure the interchange of 
oxygen and carbon dioxide. The hydra 
plain their work. an d ear thworm use the entire surface of 

the body in this process; the fish has special organs, the 
gills, while the frog and man have lungs. 

443 



Figure 392. — The Lungs and 
Heart. 

Note the branches of the 
bronchus and blood vessels on 
the right side. 


Figure 393. — Cili¬ 
ated Epithelium. 
Such cells line our 
bronchial tubes. Ex- 











444 


RESPIRATION AND EXCRETION 


Student Report on Respiration 



Get Oxygen 

Get Rid of Car¬ 
bon Dioxide 

Breathe Through 


Water 

Air 

Water 

Air 

Skin 

Gill 

Lung 

Air 

Tubes 

Leaves 

Amoeba 

Crayfish 

Fly 

Clam 

Toad 

Bird 

Man 

Bean 

Yeast 











Organs of Respiration in Man. -— Air enters the nose and 
passes into the windpipe or trachea (tra'ke-a). The opening 
into the windpipe is covered by the epiglottis (Greek, epi, 
upon; glotta, tongue), which is raised during breathing and 
closed when food is swallowed. The windpipe divides into 
two branches, one entering each lung. Each branch is called 
a bronchus. The windpipe and bronchi are the air passages 
which carry air to the lungs. These passages are kept open 
by numerous stiff cartilage rings, which, in the trachea, are 
not entirely complete on the side of the esophagus, and in the 
smaller tubes even less so. 

On entering the lung each bronchus divides into branches 
which in turn branch out again and again, until the entire 
lung is penetrated in all its parts by these passages. Finally 
each branch ends in a small pouchlike sac called an air cell. 
The walls of the air cells are thin, and the cells themselves 
are surrounded by minute branches of the blood vessels. 
It is estimated that the highly folded condition of the walls 
of the bronchi make a surface larger than the entire surface 
of the body. All these thin walls of the lungs and blood 






















BREATHING 


445 


vessels are adapted to the passage of oxygen into the 
blood. 

The lungs of man, then, consist of two large bronchial 
air tubes, many branches of the bronchi, air cells, blood 
vessels, and a few nerves, all bound up into two definite 
bodies (Figure 392). 

The voice box or larynx (lar'inks) is found just below the 
opening into the windpipe and is called “ Adam’s apple.” 
The larynx is formed by several large pieces of cartilage 



Figure 394 . — Voice Box or Larynx. 

lined with a mucous membrane. On the inside of the larynx 
project two folds of elastic tissue which are called the vocal 
cords. 

354. Breathing. — The lungs are elastic and can be 
squeezed like a sponge. Inspiration is the term applied 
to the taking of air into the lungs, and expiration to the 
forcing out of air. When air is drawn into the lungs, the 
chest expands, and the diaphragm (Figure 395), the horizontal 
muscle which divides the lung cavity from the abdomen, is 
drawn down. Thus the chest cavity is enlarged and air is 
sucked into the lungs. In expiration the air passes out gently. 

When we breathe naturally, only a small part of the air 
in the lungs is exchanged at each inspiration and expiration, 







446 


RESPIRATION AND EXCRETION 


but by breathing deeply a few times we can remove the larger 
part of the air from the lungs and replace it with fresh air. 

The natural rate of breathing is about eighteen times a 
minute, but the rate is higher in persons with a small lung 
capacity. Exercise increases the rate of breathing. Ex¬ 
plain why exercise out-of-doors is 
better for us than that taken in¬ 
doors. 

All the air passages are lined 
with cells bearing numerous cilia 
(Figure 393), and these cilia are 
constantly in motion. Their work 
is to carry toward the mouth the 
particles of dust and other foreign 
materials brought in by the air. 
This foreign matter is removed 
when we cough or clear our throats. 
Explain why clean air is better for 
us than foul air. 

The purpose of respiration is to 
take the air, rich in oxygen, into 
the lungs, where the oxygen passes 
into the blood as the capillaries 
penetrate the walls of the lungs, 
and to give off the waste carbonic 
acid gas that has come from the 
cells of the body. Thus respiration is a twofold process, the 
supplying of the living cells of the body with oxygen and the 
removal of wastes from the blood. The air that is inhaled 
contains a small amount of carbonic acid gas, but the pro¬ 
portion is much smaller than in the exhaled air. It is well 
to keep in mind that green plants are constantly, during the 
daytime, using carbonic acid gas in manufacturing starchy 
foods and giving off oxygen so that the air is being made 
better for animals and man to breathe, while at the same time 



Figure 395. — Diagram to 
Show the Relation of the 
Diaphragm to the Ribs. 


Between the ribs are shown 
some of the intercostal muscles 
that assist in respiration. 









BREATHING 


447 


these green plants are storing up food for animals, including 
man. 




Ventilation. — Associated with the question of breathing 
is the problem of supplying our homes with fresh, pure air. 
Every one feels better after a walk in the open air. How to 
have plenty of fresh air in our rooms is a difficult problem. 
One of the difficulties is 
to get the air down to 
the breathing line and 
not stir up the dust on 
the floor. Figures 396 
and 397 show the best 
plans for ventilating a 
room. They are adapted 
to the two common meth¬ 
ods of heating, hot air 
and steam or hot water. 

They show the course 
taken by the currents of 
fresh air entering the 
room at night with the 
window open, and in the 
daytime with it shut. 

Exercise. — Even if the 
home is furnished with 
fresh air, we should ob¬ 
serve good habits of 
breathing. When we 
walk out-of-doors, we should take plenty of fresh air into our 
lungs in a series of deep breaths. All young people should 
take exercise in the open air, because such exercise develops 
all the organs and makes them strong. Thus the whole 
body becomes more robust and better able to withstand 
disease and to do its work. 

Suffocation. — When the body is deprived of a sufficient 


Room at f//s//r 

/HD/RECr HEATWS. 


Room /A/Z>AYr/M£ 

MOMECE HEAT MG. 

Figure 396 . — Hot-air Heating. 
By Earl Hallenbeck. 


























448 


RESPIRATION AND EXCRETION 


supply of oxygen, suffocation results. This is what happens 
in drowning or when the windpipe becomes closed. 

In many cases a person who is suffocating may be saved 
through artificial respiration. This is the name given to 
a series of movements which are used to restore natural 
breathing. The simplest method is to place the patient on 

his back, with the head 
lower than the hips. 
Then raise the arms up¬ 
ward and outward until 
they come together above 
the head. This move¬ 
ment enlarges the chest 
cavity and helps to draw 
air into the lungs. The 
air is forced out of the 
lungs by bringing the 
arms back to the side of 
the body and pressing 
gently against the sides 
of the chest. This series 
of movements should be 
repeated gently every few 
seconds, and may have 
to be continued for two 
or three hours before 
natural breathing is re¬ 
stored. 

Diseases of the Respiratory Tract. — The most common 
of these diseases is a cold located in the nose and throat. 
The nasal passages become clogged with mucus which con¬ 
tains many germs. These germs are widely distributed in 
sneezing. 

Diphtheria is a germ disease which is located in the 
throat and nose. For many years diphtheria was one of 




Room /a/D^vmme 


D/RE CT HE A T/A/G 

Figure 397 . — Steam Heating. 
By Earl Hallenbeck. 
















BLOOD 


449 


the most deadly of our diseases, but through the use of the 
diphtheria antitoxin the danger has been greatly reduced. 

Bronchitis and pneumonia are germ diseases located in the 
bronchial tubes of the lungs. Pneumonia is a frequent 
cause of death among aged people. 

Tuberculosis of the throat and lungs is a widely distributed 
disease which causes many deaths each year. See page 489. 

Adenoids are the result of an enlargement of the pharyn¬ 
geal tonsil. The commonest result is the stopping of the 
nasal passage. Almost all mouth¬ 
breathing children have adenoids. 

These should be removed not only be¬ 
cause they prevent the natural use of 
the nasal passage but because they 
often cause deafness. 

355. Blood. — The blood is the fluid 
which circulates through the heart, 
arteries, and veins, supplying nutritive 
material to all parts of the body. 

Blood is made up of a fluid (plasma) 
which contains cells or corpuscles 
(Latin, corpusculum, little body). The 
blood cells or corpuscles are of two 
kinds, red and white. 

The red corpuscles are colored with a substance called 
hcemoglobin (he-mo-glo'bm: Greek, haima, blood; globus, 
ball). When a few of these corpuscles are examined through 
a microscope, they appear yellowish instead of red ; but when 
a large number of them are seen in a mass, the red color is 
apparent. When the red cells are first formed, they have a 
nucleus which gradually disappears. As a result, the mature 
red corpuscles, unlike all the other cells we have studied thus 
far, have no nucleus. Red corpuscles are about 3 aVo 1 an 
inch in diameter and t^too °f an i n °h thick. 

The red corpuscles carry oxygen from the lungs to the 



Figure 398 . — Photomi¬ 
crograph of Blood of 
Frog. 

The minute black spot 
in each corpuscle is the 
nucleus. The nucleus is 
absent in human red blood 
corpuscles. 




450 


RESPIRATION AND EXCRETION 



cells of the body. As soon as the oxygen in the respired air 
enters the blood, it unites chemically with the haemoglobin 
contained within the red blood corpuscles. Here it remains 
until it reaches cells that are deficient in oxygen, when it 
passes from the blood by osmosis to such cells. These cells 
take the oxygen and use it in the process of oxidation, which 
goes on continuously in every living cell. A good supply 
of red blood corpuscles is, therefore, necessary, if the cells of 
the body are to have a sufficient supply of oxygen. The 

feeding of the cells with 
oxygen is one part of 
respiration. 

At the same time that 
oxygen is received from 
the blood by the body 
cells, carbon dioxide is 
given off. Again osmosis 
explains the method of 
this transfer. Most ' of 
the carbon dioxide' is 
carried by the plasma, 
although some of it unites 
with the haemoglobin. 

White blood corpuscles are much like the amoeba in that 
they are colorless and can change their form. They move 
about in the body and often leave the blood vessels and col¬ 
lect at one place to aid the body in destroying disease germs. 
The white blood cells eat these disease germs in just the same 
manner that the amoeba or paramecium eats bacteria. 

The blood plasma is straw-colored and varies in composi¬ 
tion from day to day, and hour to hour. It contains the 
foods on their way to the cells and waste products on their 
way to the kidneys, lungs, or skin. 

The volume of blood in the average person is about six 
quarts. 


Figure 399. 

As the blood flows through the capil¬ 
laries which are found in all voluntary 
muscles, for example, oxygen and other 
food products are given off to the muscle 
cells, and carbon dioxide and other waste 
substances pass off from these same 
muscle cells into the capillaries on the 
way into the veins. 








HEART AND BLOOD VESSELS 


451 


356. Clotting of Blood. — When the blood is exposed to the 
air it forms a clot. This 
is a peculiarity of blood 
alone. If it were not for 
this property of blood, 
animals would bleed to 
death from even a slight 
cut. In some warm 
blooded animals, the 
blood clots more quickly 
than in man. Man is 
able by pressing upon 
the blood vessels or by 
tying them to assist the 
process of clotting and 
prevent hemorrhage 
(hem'or-rag). Natu¬ 
rally the blood does not 
clot except when ex¬ 
posed to the air when 
fibrin threads are formed 
from the fibrinogen (fl- 
brin'o-jen) of the plasma 
of the blood. These 
threads hold the red and 
white corpuscles. After 
a short time the whole 
mass shrinks, squeezing 
out the fluid part of the 
blood, and the semi-fluid 
mass that remains is the 
clot. 

0 __ T _ , , , Figure 400 . — Organs of Circulation. 

357. Heart and Blood w . ,, , 

. Veins, black; arteries, with transverse lines. 
Vessels. I he blood IS L e ft s^g 0 f fig ure shows superficial vessels, 
carried from the heart while right side shows deeper vessels. 














452 


RESPIRATION AND EXCRETION 


to all the cells of the body and back to the heart again and 
again. The heart serves as a pump to force the blood along. 
The heart is about the size of the fist and has strong muscu¬ 
lar walls. In a healthy person, it contracts regularly about 

seventy times a minute. It is 
obvious, therefore, that the work 
which the heart does is very 
great . 1 

The heart is located in the 
thoracic , or chest cavity, a little 
to the left side and between the 
lungs. It is a cone-shaped or¬ 
gan, inclosed in a membranous 
bag called pericardium (per-i- 
kar'di-um : Greek, peri, around ; 
cardia, heart). 

The heart is divided by a wall 
into right and left chambers. A 
nearly complete cross partition 
divides each side into upper cham¬ 
bers, the auricles, and the lower 
ones, the ventricles. The opening 
between an auricle and a ventricle 
is guarded by a valve, which is 
partly membranous and partly muscular. The auricles 
receive blood from the veins, while the ventricles force 
blood into the arteries. 

Artery is the name given to the blood vessels which carry 

1 “The work the heart does during the day is about equal to the energy 
expended by man in climbing to the top of a mountain 3600 feet high. 
Assuming that the man weighs about 150 pounds, this would be equal to 
an amount of energy sufficient to lift 90 tons to a height of three feet. The 
work of the left side is greater than that of the right, since the former has 
to drive the blood all over the body, while the latter has only to force it 
to the lungs which are near by. For this reason the muscle walls of the 
right ventricle are much thinner than those of the left ventricle.” — Conn 
AND BUDDINGTON. 



R . V, right ventricle; L. V 
left ventricle ; R. A., right auri¬ 
cle ; L. A., left auricle. The 
arrows indicate the direction 
that the blood takes. Describe 
its course through the heart. 





HEART AND BLOOD VESSELS 


453 






Figure 402 . — Dia¬ 
gram of a Vein 
Showing the 
Valves. 

In which direc¬ 
tion does the blood 
flow in this dia- 


blood from the heart, and vein is the term applied to the 
vessels which return blood to the heart. There is little 
structural difference between the veins and arteries except 
that the walls of the arteries are thicker, 
and there are no small valves as in the 
veins. As the branches of the arteries be¬ 
come minute, the walls become much thinner, 
thus allowing the food and oxygen to pass 
more easily to the individual cells. These 
minute branches are called capillaries (Latin, 
capillus, hair). From a cluster of capillaries 
a small vein begins which soon connects 
with a slightly larger vein, which leads back 
to the heart through larger and larger veins. 

The blood follows a regular course through 
the body, passing from the left ventricle into 
the aorta , which is the largest artery in the 
body. As soon as the aorta leaves the heart, 
smaller arteries branch from it, and the aorta 
itself also branches until the entire body is 
supplied with blood. The right ventricle gives off 
artery which divides, a branch entering each lung, 
point where an artery leaves a ventricle, there are three half- 

moon-shaped valves which 
prevent the blood from 
flowing back into the heart 
(Figure 402). 

The blood which is car¬ 
ried into the lungs con¬ 
tains a large amount of 
carbon dioxide which gives 
it a dark color. In the lungs the carbon dioxide is given 
off and oxygen taken up, so that when this blood is returned 
to the left auricle, it is of a bright red or “ arterial ” color. 

Every time the heart beats the blood is forced into the 


gram ? 


a short 
At the 



Figure 403 . — Diagram of Capillaries. 

The artery breaks up into minute 
branches, the capillaries, which in turn 
unite to form veins. 







454 RESPIRATION AND EXCRETION 

arteries in waves which can be felt in the wrist or neck by 
placing the finger over an artery. The wave is called the 
pulse. By counting the number of waves each minute, the 
rate at which the heart beats is determined. When a person 
runs or takes violent exercise, the pulse rate increases. It 

is advisable to know what our 
usual pulse rate is, for an in¬ 
creased pulse rate is sometimes 
an indication of approaching 
illness. 

Closely associated with the 
pulse is the additional condition 
known as blood pressure. Blood 
pressure is the force with which 
the blood pushes against the 
walls of the arteries with every 
heart beat. Special appliances 
have been devised which accu¬ 
rately measure the amount of this 
pressure. The information thus 
revealed to the skillful physician 
is often very important. 

Lymph. — As the blood flows through the capillaries, 
part of the plasma passes through the thin walls into the 
spaces between the cells and bathes the cells. This fluid 
which escapes from the capillaries is called lymph (limf). 
It is composed of digested food, water, and other substances. 
The cells assimilate the food which they need and cast back 
into the lymph the wastes which they have formed in the 
process of growth and repair. These spaces between the cells 
are small and irregular in shape. The spaces, however, form 
a sort of mesh, or net, the parts of which join, forming larger 
vessels, and finally all the lymph is collected into two large 
vessels which open into veins. Thus there is the lymphatic 
circulation which differs from that of the blood in several 



To Kidneys^-'i. 


/To Large Intestine- 
..-To Leg 


Figure 404 . — Main Arteries 
of Frog. 








HEART AND BLOOD VESSELS 


455 


ways. (1) There is no special organ for forcing the lymph 
along, the circulation depending mainly upon the movement 
of the muscles. (2) The lymphatic vessels are imperfect in 
the beginning, being only irregular spaces. (3) The lymph 
contains no red corpuscles and only a few white corpuscles. 

Cuts. — Since every part of the body inside the skin is 
traversed by blood vessels, we 
cannot injure any part without 
breaking some blood vessels. A 
small cut causes the blood to flow 
only from capillaries, and it flows 
slowly and in small quantities. 

If a vein be cut, the blood will be 
dark in color, and will flow in 
larger quantities, but steadily. 

A severed artery sends out bright 
red blood in waves corresponding 
to the beat of the heart. To stop 
the flow of blood from a vein, 
compress the vein beyond the 
cut; from an artery compress the 
artery between the cut and the 
heart. In either case remain quiet 
to aid the blood to form a clot. 

Exercise. — The object of a cir¬ 
culatory system and of a circula¬ 
tory fluid is to supply every cell 
in the body with food and to 
carry away the waste. The more 
active the process of circulation, the more perfectly is this 
object accomplished. It is the common experience that the 
heart beats more rapidly, the lungs work harder, and the 
body becomes warm after a few minutes of vigorous exer¬ 
cise. These changes have a decidedly beneficial effect upon 
building up the body and removing the wastes. 



Figure 405. — Main Arteries 
of Man. 


Compare with Figure 404. 






456 


RESPIRATION AND EXCRETION 


Fainting. — Fainting is due to an insufficient supply of 
blood in the brain. This lack of blood may arise from 
several causes, but the most common is some disturbance 
of the digestive processes, which causes the heart to beat 
too slowly. A fainting person should be placed flat on 
his back, if possible, with his head slightly lower than the 
rest of his body, and should be given plenty of fresh air. 
A dash of cold water in the face, or a bottle of ammonia 
held to the nostrils, is often helpful in restoring consciousness. 

The Effect of Drugs and Alcohol. — “ The flow of the 
blood is modified by various drugs, some causing the blood 
to flow more rapidly, others more slowly. Coffee causes 



Figure 406. — Superficial Lymphatics of Arm and Hand. 


the heart to beat harder and at the same time causes some 
of the arteries to become smaller. For this reason it is 
called a stimulant.” — Conn and Buddington. 

It has been stated frequently that alcohol increases the 
activity of the heart. Careful experiment, however, shows 
that not only is the effect not that of a stimulant, but that 
when used in large amounts, it markedly weakens the action 
of the heart. If taken only in small amounts, the heart 
sometimes shows a slight increase in its rate of beating, 
but this occurs only when the brain becomes excited, and if 
the person is kept quiet no change in the heart beat is notice¬ 
able. Thus the primary action is on the brain. 

“ A second effect of alcohol is more evident. The small 
blood vessels in the skin are enlarged. This produces a 











EXCRETION 


457 


flushed skin, a feeling of warmth, and a false feeling of in¬ 
creased circulation. Its result is to send more blood through 
the skin with consequent extra loss of heat. This action 
is evidently not due to stimulation, but to the relaxation of 
the muscles, and is thus a decrease of activity rather than an 
increase, even though the blood does flow a little more rapidly 
through the skin. These facts make it clear that alcohol 
cannot be properly called 
a stimulant of the circula¬ 
tory system.”— Conn and 
Buddington. 

358. Excretion. — Every 
animal uses energy in carry¬ 
ing on its work. During 
this process a certain amount 
of waste substance is pro¬ 
duced, which has to be re¬ 
moved from the body. The 
skin, kidneys, and lungs are 
the chief organs which assist 
the body in getting rid of 
this waste. When any part 
of the living cells is broken 
down in the simple act of 
living, a waste product re- Figure 407 . —Longitudinal Section 
suits. By osmosis these 

waste products enter the blood and are removed by the 
lungs, which give off carbon dioxide, by the sweat glands 
in the skin, and by the kidneys, which remove the wastes 
that contain nitrogen. The sweat glands and kidneys are 
usually regarded as the excretory organs of man. These 
organs remove from the blood the wastes which have been 
excreted by the cells of the body. The excretion from the 
living cells is one of the fundamental life processes of all 
plants and animals. This form of excretion should not be 




458 


RESPIRATION AND EXCRETION 


confused with the indigestible part of the food which is not 
taken up by the blood and which passes out through the large 
intestine as faeces. 

The kidneys are two bean-shaped organs located in the 
abdominal cavity, one on each side of the “ small ” of the 
back. Each is about four inches long, two and a half inches 
wide, and half an inch thick. The color is a dark red. The 
kidney is made up of two layers, the outside or cortical, and 
the inside or medullary. Each layer is composed of many 


Artery 



uriniferous 

tubule, 

Figure 408 . — Diagram. 
Showing relation of artery and 
vein to portion of minute kidney 
tube (uriniferous tubule). 


small tubes (tubules) which 
open into an area called the 
pelvis , 1 the space within the 
kidney. The pelvis continues 
into a duct (ureter), and from 
each kidney the ureter passes 
into the bladder. A* small 
duct (urethra) (u-re'thra) con¬ 
nects the bladder with the 
exterior of the body. 

Each tubule in the kidney 
is in close relation with the 
blood capillaries. At the 
place where this close relation is found, glomerulus (glo-mer'u- 
lus), the walls of the capillary and the walls of the kidney are 
very thin. Through these thin walls a large amount of water 
filters out of the blood into the tubes. At the same time 
waste material which contains nitrogen, salts, and other 
organic wastes is removed. If these wastes are not removed, 
they create toxins which poison the body. 

Skin. — The skin covers and protects the voluntary 
muscles, regulates the body temperature, gives off waste 
matter, and acts as a general sense organ. Thus we see that 
it is incorrect to think of the skin simply as an organ of 

1 The word pelvis is also used in referring to the hip bones, and it is better 
to call the latter structure the bony pelvis. 




EXCRETION 


459 


excretion. In order to understand just how wastes are 
removed by the skin, it is necessary to study its parts. The 
outer layer of the skin is called the epidermis (Figure 409) 
and is chiefly composed of dead cells. These outer cells are 
constantly breaking off, a process which is most apparent 
in the case of sunburn. Whatever pigment or coloring 
matter there is in the skin is located in the inner cells of the 
epidermis. The amount and kinds of pigment determine 
whether a person is of light or dark complexion, white, black, 
or yellow. These inner 
cells are constantly grow¬ 
ing new cells to replace 
the cells which scale off. 

The nails and the hair 
arise in the outer layer of 
the skin. Other structures 
which arise in the same 
way are the scales of fishes 
and snakes, the hoofs and 
horns of cattle, and the 
feathers of birds. 

The inner layer of the 
skin is the dermis; it con¬ 
tains blood vessels, nerves, 
connective tissue, the sweat glands, and sense organs of 
touch, pain, heat, and cold. It is estimated that there are 
over two million sweat glands in the skin of man. These 
are the excretory organs of the skin and their work is to 
eliminate waste substances from the blood and to keep 
the body temperature normal (98.4° F.) by regulating the 
amount of perspiration excreted. The amount of perspira¬ 
tion is influenced both by the temperature of the body and 
the air. The evaporation of perspiration keeps the body 
at the normal temperature. 

The skin is attached to the body by a loose layer of con- 



Figure 409 . — Diagram of Skin. 














460 


RESPIRATION AND EXCRETION 


nective tissue in which fat is deposited. This is known as 
the subcutaneous layer of fat. This layer becomes very 
thick in corpulent people. 

Leather. — The study of the skin which we have just made 
introduces us to some interesting biological problems con¬ 
nected with one of our commonest possessions — shoes. 
The skin of man is built upon the same plan as the skin of the 
animals from which the leather used in shoes, harnesses, grips, 
and gloves is manufactured. This large industry depends 
upon the structure of the skin, especially the arrangement of 
the fibers in the dermis. In the skin of a fish or an alligator, 
the fibers of the dermis run parallel and at right angles in the 
several layers, while in the hairy animals these same fibers do 
not follow any order of arrangement, which results in the 
production of a felt-work of interlacing fibers producing a 
strong skin which resists tearing or flaking. 

Most of the leather that is used in shoes to-day is from 
the hides of cattle. Great numbers of these animals are 
slaughtered each year for food. Their hides must be removed 
with care so as to avoid cutting, as all such injuries destroy 
the fibers of the dermis. These hides are then sent to tanner¬ 
ies where each is made into a certain grade of leather, such as 
sole leather or the leather for the upper part of the shoe. 
This difference in thickness and firmness is produced largely 
by the method employed in tanning. When a vegetable 
tan is used, such as hemlock bark, oak, or sumac, sole leather 
results; and when a mineral tan is employed, leather suit¬ 
able for the upper part of the shoe is secured. 

Two common parasites, the white grub and the southern 
cattle tick, live in the skin and render it unfit for 
leather so that it is to the advantage of cattle breeders to 
keep their cattle free from these parasites. The United 
States Department of Agriculture has greatly assisted cattle 
raisers in exterminating these destructive parasites. The 
effort to exterminate the parasites, especially the southern 















W. T. Sedgwick (1855-still living), head of the Department 
of Biology and Public Health at the Massachusetts Institute of 
Technology, has devoted his training and energy largely to 
making cities healthful. He is one of the foremost American 
biologists in making investigations upon milk, water, sewage, 
and epidemics of typhoid fever, and in showing how to apply 
these technical studies to human welfare. 

He was one of the first to study the bacteria of the air, and 
his work on the “ Principles of Sanitary Science and Public 
Health” (1902) was an important contribution to public health 
education. In addition to this marked service to his countrymen, 
he has devoted his life to teaching biology and sanitary science 
and to training biologists and public health workers. 

One renders a great service to his age who leaves the world 
safer to live in than he found it. 





EXCRETION 


461 


cattle tick, was so successful that in 1918 hides valued at 
many millions of dollars were added to the general supply 
in the United States. Another biological factor in the pro¬ 
duction of good leather has reference to the care that the 
cattle receive. If they are well fed and properly housed 
during the winter and keep free from disease, then their 
hides have a better texture and are finer grained. The 
coarser grades of leather are made from older cattle and those 
that have little or no shelter in winter. Man has never been 
able to originate or create leather. It must be first grown as 
the skin of some animal. Man’s skill consists in his manipu¬ 
lations of the hide after a living animal has grown it. 

Sewage. — In every town and city where a general water 
supply is established, it is necessary to provide means for the 
removal of the waste water. This water comes from homes, 
places of business, and various manufactories. Not only 
the wastes from the human body but also from the street 
washing, the waste products of various factories, and the 
annual rainfall and snow are all added to the waste waters of 
a city or town. Such water is known as sewage. A great 
deal of study is being given to this problem that becomes more 
and more difficult as the number of people living in a given 
place increases. 

It is now known that there is an average of one hundred 
gallons of sewage daily for every inhabitant of a city. The 
daily sewage from homes averages about thirty gallons for 
each member of a family; but when we add the street flush¬ 
ing and wastes of various manufactories the total amount 
per capita is not far from the larger amount named. Thus 
in a city of 100,000 inhabitants, there will be about ten million 
gallons of sewage a day. What must be the daily average 
of sewage in your city? 

Disposal of Sewage. — The question of what shall be done 
with all this vast amount of sewage is one of the most 
difficult that cities are trying to solve. The cities that are 


462 


RESPIRATION AND EXCRETION 


located on or near the ocean or Great Lakes let their sewage 
run into them. Those that are built on a stream or river 
empty into this small body of water and the town or city 
farther down the stream does the same. Smaller towns that 
are not located upon any body of water have installed fil¬ 
tration plants. These are very effective where the total 
amount of sewage is small. Where does the sewage of your 
city or town go ? 

Stream Purification. — Some recent studies made under 
the direction of the Massachusetts Institute of Technology 
show that there are a number of biological factors that assist 
in the purification of sewage polluted water. These are a 
number of organisms that feed upon the organic matter that 
is suspended in the water. The first living things to be found 
where the water is most polluted are bacteria. As the 
sewage empties into the stream it is rich in food for bacteria 
and they become very numerous. As they feed upon this 
food, it is broken up into simpler chemical bodies and the 
water becomes clearer. A little farther away from the mouth 
of the sewer, are found numerous protozoa that feed upon 
these bacteria and thus tend to remove them from the water; 
while still farther down the stream, are to be found numerous 
tube-bearing worms that in turn feed upon the protozoa. 
If the water is now examined, it is found to be much clearer 
for most of the sediment has either settled to the bottom 
or been destroyed by these several organisms. Such water 
as this is not fit to drink. 

Water Supply. — Plenty of pure water for drinking and 
cooking is indispensable to man. The necessity for disposing 
of the sewage has made this problem increasingly difficult. 
Sewage-polluted water is never entirely safe for drinking 
water. The two must be kept separate. This is the main 
reason why so much money has had to be spent to bring our 
drinking water to the cities and this is the reason why so 
much care is taken to prevent this same drinking water from 


EXCRETION 


463 


becoming contaminated. Some of the smaller towns have 
not yet come to appreciate the value and importance of hav¬ 
ing pure water to drink. The result is frequent epidemics of 
sickness. 

In Figure 410 is shown a model reservoir for a small town. 
The reservoir is located on a high piece of ground and all 
possible sources of surface drainage have been eliminated. 
The surroundings are graded so that standing water cannot 



Figure 410. — A Model Reservoir. 


accumulate and become impure to flow later into the reser¬ 
voir. In Figure 411 is shown a reservoir in which the con¬ 
ditions are the reverse. The water is stored in a place sur¬ 
rounded by residences and swampy ground on the left of 
the photograph. The open channels in the grass are streams 
that empty into the water of the reservoir. One of these is 
supplied from the overflow of water of the Erie Canal. This 
alone is sufficient explanation of why there have been fre¬ 
quent epidemics in the town that has this water supply. 
What are the conditions surrounding the water supply of 
your home ? 

In the country, the water is taken from wells and springs, 
which are splendid sources of water when properly protected 



464 


RESPIRATION AND EXCRETION 


from the drainage of the house and barn. But people in the 
country are not as alert as those in the city and do not give 
as much attention to this important aspect of preserving 
their health as they should. In fact a great many people in 
the city would give no attention to it, were they not com¬ 
pelled to do so by the health laws of their state. Because 
uniform laws are being enforced in our cities and larger towns, 
these places are more healthful to live in than the country 



Figure 411. — A Poor Reservoir. 

Note the open stream that empties into the main body of water. The 
impure water of the Erie Canal drains into this open stream. 


where each one is a law unto himself so far as protecting his 
water supply is concerned. Many people do not understand 
how water can be impure when it looks clear and there is no 
sediment. Nor do they comprehend that the air likewise 
can be impure although it looks clear. We shall soon learn 
that through the studies of technical scientists, there have 
been discovered organisms, which cause sickness, that are so 
small as scarcely to be visible with a microscope. These 
minute organisms live in the air and water and one cannot tell 
anything about the purity of the air or water by looking at it. 





QUESTIONS 


465 


SUMMARY 

All living things breathe oxygen which, in man and the 
higher animals, is carried by the blood to the cells of the body. 
The parts which man uses in breathing are more highly 
developed than in any other animal. Man has a voice box, 
the larynx, by means of which he is able to make a wide 
variety of sounds. The blood of man is similar to the blood 
of all other vertebrates, although not identical. It consists 
of red and white corpuscles which move freely in the plasma. 
The blood is confined in the blood vessels through which it 
is forced by the heart. Excretion includes the waste products 
derived from the living protoplasm. The lungs, the sweat 
glands of the skin, and the kidneys remove this waste from 
the blood. The care of waste requires that we give increas¬ 
ing attention to the question of sewage and water supply. 

QUESTIONS 

Compare the respiration of man, the hydra, and the earthworm. 
Compare the lungs of man with the gills of a fish. What is blood? 
What are its uses ? What is the difference between veins and arteries ? 
Explain the work of the skin and kidneys. What is sewage? How 
is it cared for in your home? city? town? Where do you get your 
water supply ? 


CHAPTER XXXIV 


THE NERVOUS SYSTEM OF MAN 

359. Parts of the Nervous System. — The nervous system 
of man consists of the same general parts as the nervous 
system of the frog (see page 88). There is a brain and 
spinal cord, from which nerves extend to the special senses, 
the muscles, the heart, and the stomach. When the brain 
of man is compared with that of the frog, it is obvious 
that the cerebrum of man is proportionately larger. Al¬ 
though some of the other parts of the brain appear unlike 
the corresponding regions in the frog, scientists tell us that 
they are really the same. 

380. The Nerve Cell. — The nervous system of man con¬ 
sists of many thousands of nerve cells which differ from all 
other cells in having more parts and branches (Figures 
413, 414, 415). Examination shows that the nerve cells 
have a prominent nucleus surrounded by cytoplasm, which 
grows out into a number of branches called fibers. The 
shorter branches divide and form, together with the branches 
from the neighboring nerve cells, a mass of tangled fibers. 
There is usually one unbranched fiber, perhaps several feet 
long, which ends either in the skin, in some muscle, or in 
the spinal cord or brain. When this long fiber reaches the 
muscle or skin, it divides into several fine branches. All 
these branches which arise from a nerve cell belong to it, and 
in this connection the word cell includes all the branches, 
the nucleus, and the cytoplasm. 

361. The Location of the Nerves. — The nerve fibers 
which have the same work to do occupy certain definite 

466 


THE LOCATION OF THE NERVES 


467 


places in the brain and spinal cord. A student of the nerves 
can tell the route which the stimulus arising from feeling 
a pencil must travel be¬ 
fore reaching that part 
of the brain where it is 
interpreted as a pencil; 
or the route over which 
the stimulus arising from 
tasting candy must pass 
before it is known to be 
that of candy. When 
we see the pencil or the 
candy, the route over 
which the sight stimuli 
of these two objects 
travel is not the same 
as that of the feeling of 
the pencil or tasting the 
candy. The nerve cells 
which interpret the 
stimulus arising from 
feeling the pencil or from 
tasting the candy or see¬ 
ing the pencil and the 
candy are probably not 
the same. We may say, 
therefore, that the spinal 
cord and brain are made 
up of many special nerve 
pathways which end in 
nerve cells that interpret 
stimuli. 

The nerves which con¬ 
nect the central nervous system, that is, brain and spinal 
cord, with all parts of the body, consist of many long nerve 



Figure 412. — Nervous System of Man. 



468 


THE NERVOUS SYSTEM OF MAN 


fibers. Each nerve looks like a small white thread and is 
covered with a thick, fatty sheath (medullary sheath). In 
the living animal, this fatty sheath is white and the nerve 
fibers so covered are found to occupy a certain part of the 
spinal cord and brain. Thus, we get the name white sub¬ 
stance. Other of the nerve fibers and cell bodies are not 
covered with a sheath and so have a gray appearance. Thus 
we have the term gray substance in connection with the 
nervous system. 

The Central Nervous System. — In Figure 412 the nerves 
of the legs, arms, and trunk are all seen to be united to a 


central body, the spinal 
cord. There are nerves 
in the upper part of the 
neck and in the head re¬ 
gion that unite with the 
large mass at the upper 
end of the spinal cord, the 
brain. The brain and 


i 



Figure 413. — Nerve Cells. 


Stained by the silver process which spinal cord are known as 


blackens all the parts. This is an excel¬ 
lent stain to show the branching processes. 


the central nervous sys¬ 
tem. The brain is di¬ 


vided into the following parts : cerebrum, the most anterior; 
the mid-brain, to which the optic nerves join; the cere¬ 
bellum ; and the medulla oblongata, to which the nerves of 
hearing, tasting, and the facial nerves belong. 

The cerebrum is the most important of the several regions 
of the brain. It regulates and controls all our nervous activ¬ 
ities. The cerebellum gives tone and vigor to the contrac¬ 
tion of the muscles and helps us to know when we are prop¬ 
erly balanced and is hence known as the equilibration center. 
The remaining parts of the brain give off and receive nerves 
and transmit nerve stimuli to the cerebrum and cerebellum. 

362. Growth of the Nervous System. — The nervous 
system of man, like all other parts of the body, has a definite 




REFLEX ACTION 


469 


beginning and grows in an ordered manner. Not only is 
this true in man, but also in the frog and fish. The tissue 
of the embryo, which is to grow into brain and spinal cord, 
gradually changes until the adult parts are formed. Dur¬ 
ing this early period of growth, the nerve cells send out 
processes which become nerve fibers, so 
that at birth the nervous system is ready 
to go to work. Indeed, nearly all the nerve 
cells which the human being is ever to use 
are made before birth. These cells gradu¬ 
ally become more active and the different 
parts of the brain work more perfectly as 
we go through the periods of childhood, 
youth, and maturity. The brain becomes 
a more perfect working organ by making 
the brain cells do their specific work over 
and over and over, until each group of cells 
can be relied upon to do a definite thing. 

363. Reflex Action. — Reflex action is 
the simplest form of nervous activity in 
man. For example, when the finger is 
placed on a hot stove and suddenly with¬ 
drawn the following actions take place. 

The heat stimulus affects the nerve end¬ 
ings in the finger and that stimulus is Figure 414— Nerve 
carried to the spinal cord. If this were Cells. 

all that occurred, the finger would burn, Stained to bring 

because this stimulus and the nerve fibers out the mmute P arts 
. . J . in addition to the 

over which it travels have no control over nuc i eU s. 

the muscles. The removal of the finger 

is brought about by another set of nerve cells — the cells 

which have their fibers ending in the muscle of the hand 

and arm. All these changes take place involuntarily, and 

the reaction to the stimulus is known as reflex action. 

Specific names are used in describing these several changes; 




470 


THE NERVOUS SYSTEM OF MAN 


the nerve fibers which connect the skin with the spinal cord 
and brain are called afferent (af'fer-ent: Latin, ad, to; 
fero, to carry) fibers because the stimulus always travels 
towards the brain. 

Their function is sensory, for they carry the stimulus to 
the brain. The fibers which connect the muscle with the 
brain or spinal cord are the efferent (ef'fer-ent: Latin, 
ex, from; fero, to carry) fibers, because they carry their 
message away from the central nervous system. Their 
function is to produce motion. In the special instance we 



Figure 415. — Diagram to Show Reflex Action. 


The stimulus comes in contact with the skin and is carried to the 
spinal cord. It then passes to the motor cells which carry the order 
to the muscle. The same skin stimulus goes to several other parts of 
the spinal cord. 

are studying, the heat stimulus causes the spinal cord to 
send a special message to the muscles of the finger, so that 
the latter is removed from the stove. 

This is a typical illustration of the simplest way in which 
the nervous system works, but in most reflex actions there 
are other results. After the finger has been removed from 
the hot stove by reflex action, we soon realize that the skin 
is burned, the realization coming through the smarting 
sensation. This second stimulus has been carried to the 
brain, and we are now conscious of the stove, heat, burn, 
etc. If there were no afferent nerve fibers, the individual 
could not experience any pain when hurt. 




REFLEX ACTION 


471 


The afferent and efferent nerves, whether in reflex or 
in general nervous action, never vary in the work which 
they do. The sensory afferent nerves form the only paths 
over which our information of the outside world travels to 
the brain. The stimuli which cause the different sensations, 
such as taste, sight, etc., have their individual paths and re¬ 
ceiving organs. This is indicated by the fact that no other 
nerves than those of the ear are ever affected when we hear. 

Reflex Action in the Frog . — The frog, like man, is able 
to act in a definite way. If any one approaches a frog 
while it is sitting on the edge of a pond, it jumps into the 
water, stirs up the mud, and then returns to the shallow 
water near the place where it entered. The frog, in this 
case, acts as if it, or its ancestors, had learned that this is 
the best way to escape enemies. While this series of acts 
is called a habit, it is really a series of reflet acts which are 
similar to the reflex action described for man, and require 
the same nerve structures. 

Reflex Action in the Earthworm. —: If a light is flashed 
on an earthworm at night, the worm will quickly with¬ 
draw to its burrow, before it can be seized. The earth¬ 
worm has no eyes, but it is able to respond to light and 
can tell the difference between night and day. It is believed 
that special nerve cells in the skin, which are connected 
with the nerve ganglia, help the earthworm to become 
aware of the light stimulus. 

Reflex Action in Hydra. — Hydra is a minute water 
animal which has no definite nervous system, but only 
a few nerve cells scattered through the body. As the 
hydra waves its arms about in the water, there seems to 
be no purpose in its motions. But if a water flea swims 
against one of the tentacles, a part or all of the tentacles 
at once begin to carry the flea to the mouth of the hydra. 
The hydra, then, without a definite nervous system, can 
carry out a definite reflex action. 


472 


THE NERVOUS SYSTEM OF MAN 


Reflex action is similar in all animals. In all these il¬ 
lustrations, it is necessary for the stimulus to be received 
by an afferent nerve, or some structure which can do the 
same work, and for the stimulus to be transformed into a 
series of purposeful movements. 

364. Sense Organs. — All the higher animals have eyes, 
ears, a nose, and a tongue. Each of these organs con¬ 
tains nerves specialized to respond to a certain definite 
kind of stimulus. The result of this specialization is that 
not only are these special sense organs complex in struc¬ 
ture, but also the region of the brain which receives their 
messages. The ear nerve responds to a stimulus of air¬ 
waves of a certain length, and we say we hear a sound. 
The eye nerve is stimulated only by light. Each nerve 
and the brain cells to which it sends its messages have be¬ 
come so specialized that practically only one kind of reac¬ 
tion takes place. For example, all stimuli acting upon the 
eye nerves are interpreted as light. 

The skin is a simpler sense organ than the eye or ear, 
and tells us of pain and touch and the difference between 
heat and cold. 

Smell and Taste. — These two senses are closely related. 
The sense of smell is located in the nose and the organs of 
smell are minute nerve cells scattered among the regular 
cells that line the nasal passageway. The olfactory nerve 
which carries smell stimuli to the brain is the shortest nerve 
in man. 

Taste has already been described in connection with the 
digestive system on page 405. 

The Eyes. — The eyes of all vertebrates have the parts 
arranged in a similar manner. The eyeball is roundish 
and is located in the eye sockets of the skull, which are 
termed orbits. There is an upper and a lower eyelid, and 
the remains of a third eyelid in the corner next to the nose. 
The front of the eye is covered by a transparent mem- 


SENSE ORGANS 


473 


brane, the cornea (kor'ne-a); and the rest of the eye is sur¬ 
rounded by a tough membrane, the sclerotic coat, or the 
white of the eye. Within the combined covering of the 
cornea and sclera are a number of structures which take 
part in receiving and transmitting the rays of light to the 
brain. 

A cross section of the eye shows two more membranes 
in close relation to the sclerotic coat (Figure 416). The 
membrane in direct contact on the inside with the sclerotic 
layer is the choroid (kfl'roid). The choroid coat is filled 
with blood vessels and pig¬ 
ment. Through this layer 
the food in the blood is 
distributed to the eye. 

The third layer or coat is 
the retina, which is com¬ 
posed of nerve cells and 
is nearly transparent. 

The cornea and these 
three layers inclose two 
chambers which are sepa- Figure 416. —Section of Eye. 
rated by the lens (Figure C, cornea; C', choroid layer; I, iris; 

416). In front of the lens 1 C ’ inner cham ber; O. C, outer cham- 
..... . ber; L, lens; O. N, optic nerve; 

a curtain-like membrane, R> retina; St sc i er otic coat. 

the iris, partly covers the 

lens, except for a round opening in the center which is 
called the pupil. The color of the eye, gray, black, blue, 
or brown, is due to the presence of pigment in the iris. The 
small front chamber is filled with a transparent fluid which 
is composed principally of water and is known as the aqueous 
(a'kwe-us) humor. The large back chamber is filled with a 
thin, transparent, jellylike fluid, the vitreous (vit're-iis) humor. 

In order that we may see any object, a pencil in our 
hand, for example, two general conditions must be present. 
The picture (image) of the pencil must be placed on the 






474 


THE NERVOUS SYSTEM OF MAN 


retina, and this picture must be carried to the brain by 
the eye (optic) nerve. When these two conditions take 
place, we see. 

As we have learned, the stimulus for the eye is always 
light. In physics we learn that the rays of light travel in 
straight lines. This fact explains why we cannot see round 
a corner. When the rays of light are made to pass through 

a glass lens, the rays 
B- which pass through the 
A ' thin edges of the lens are 
bent and do not travel 
Figure 417. —How We See the Pencil. to foe same p l ace they 

would have reached had they not passed through the lens. 
In the same way light rays from an object pass through the 
lens in our eyes and are bent. This results in the image of 
the object, the pencil in this instance, being inverted on the 
retina. The light rays of the pencil stimulate the nerve 
cells in the retina, and this stimulus, after being carried to 
the brain, is interpreted to us as a pencil, though we do not 
know how stimuli travel on nerves. 

The inverted image of the picture on the retina is due to 
the shape of the lens. When the stimulus reaches the living 
cells of the retina and through them is passed on to the optic 
nerve and the brain, a series of changes takes place in these 
living cells. There is no evidence as to how an inverted 
or upright picture passes through these living cells in the 
retina and brain. We do know that we have to learn the 
meaning of all stimuli. For example, a baby reaches for 
things far beyond the length of its arms and it is only after 
many trials that it eventually acquires precision in reaching 
for an object. It is probable that each one of us passed 
through a similar stage of learning to interpret the stimuli 
that arose from light. In coming to understand light stimuli, 
the sense of touch was of great assistance. Try to explain 
how this would be so. 




SENSE ORGANS 


475 


Care of the Eyes. — The eyes are our most precious sense 
organs, and as such they should receive the best of care. 
Certain imperfections in the lens or other parts of the eye 
can be helped by the use of glasses. If your eyes annoy 
you, or if you cannot see objects as clearly as your school¬ 
mates, have a competent oculist examine and treat them. 

The Ear. — The ear is a sense organ for the reception 
of the stimuli which we interpret as sounds. The ear of 
man consists of the outer, middle, and inner ear. The 
first two carry the stimuli to the 
third, where they are received by 
nerve cells and carried to the brain. 

The diagram of the ear (Figure 
418) shows the several parts and 
their relations. The outer ear 
leads to the tympanic (tim-pan'ik) 
cavity; the middle ear is in com¬ 
munication with the mouth, and 
the complex inner ear is partly 
shown. There is a group of small 
bones in the middle ear which con¬ 
duct the sound vibrations to the delicate inner ear. The 
internal ear receives the various sound waves, and transmits 
them to the brain, where they are explained as sounds. 1 

Hearing. — Sound waves strike the ear drum (tympanic 
membrane), which in turn causes the small bones in the 
middle ear to vibrate. The bones cause the water in the 
internal ear to move, thus stimulating the nerves of 
hearing. 

The pressure of air on each side of the ear drum is nor¬ 
mally the same. This is due to the entrance into the mid¬ 
dle ear of air from the mouth, through the eustachian tube 



Figure 418.— Plan of Ear. 

0. E, outer ear; M. E, middle 
ear; I. E, inner ear; Eu, eu¬ 
stachian tube. 


1 When certain parts of the ear (semicircular canals) are injured, one has 
difficulty in standing or in walking erect. This is because the inner ear 
serves both as a hearing and a balancing organ. 





476 


THE NERVOUS SYSTEM OF MAN 


(see page 406). This tube is a trifle more than an inch 
long. When it becomes closed, partial deafness results. 

Defects in hearing may be caused by blows upon the 
ears, by the accumulation of wax in the ears, and by sore 
throat. When there is a continued ringing or hissing sound 

in the ears, consult a doctor 
at once. 

385. Brain Efficiency. — 

While the efficiency of the 
brain depends upon mental 
training, in order properly to 
exercise the many functions 
of this organ at least three 
things are necessary: good 
food, sufficient sleep, and 
abstinence from alcohol and 
tobacco. We have already 
discussed the question of 
food (page 410). 

The amount of sleep which 
grown people need depends 
in part upon the kind and 
amount of work they do. 
But all young people require 
a large amount of sleep. 
Children from seven to ten years of age need at least twelve 
hours of sleep every night, while youths of high school age 
need at least nine hours, and ten would be better. 

At a baseball game, you have noticed a boy catch a “ fly ” 
when it looked like a “ home run/’ or how enthusiastic 
the crowd became when the pitcher struck out the last 
man with the bases full. The nervous system of both players 
was efficient in a critical test. 

We all ride on the street cars or railroads, but do you 
know that most of the men who run the street cars and 


SKILL AND ENDURANCE IMPAIRED 
BY DRINK 

Tests in Target-Shooting in Swedish Army 
I. SKILLED TESTS 

Thirty shots fired in quick succession 
Non-Drinking Days: Average 24 hits out 
of 30 shots 

Drinking Days: Average 3 hits out of 
30 shots 


Alcohol taken equal to amount in to 2 
pints of 5 per cent beer, 20 to 30 minutes 
before shooting, and an equal amount the 
night before 

II. ENDURANCE TESTS 

Non-Drinking Days: 360 shots fired be¬ 
fore exhaustion 

Drinking Days: 278 shots fired before ex¬ 
haustion 


Alcohol taken 30 minutes before test was 
amount contained in about 1*4 pints of 
4 per cent beer 


Figure 419. 



BRAIN EFFICIENCY 


477 


trains have to pass an examination to determine whether 
they can be trusted to do their work properly and well; 
i.e., whether their nervous systems will stand the test? 
Among the questions which their prospective employers 
are sure to ask is, “ Do you use alcoholic drinks? ” 

In order to judge the success of a piece of work we must 
consider the quality and speed with which it is done. Krae- 
pelin made the following experiment, the results of which 
show that both these elements in mental work are influ¬ 
enced by the use of alcohol. 

Several men who were allowed to drink no alcohol uti¬ 
lized half an hour daily for six days in adding figures. Their 
ability to add increased 
each day. On the seventh 
day the work was begun 
under the influence of al¬ 
cohol. In spite of the skill 
gained in the previous 
practice, their accuracy 
did not increase, but on 
the contrary began to de¬ 
crease rapidly. On the 
nineteenth day the use of 
alcohol was stopped, and 
immediately an improvement in the work manifested itself; 
but on the twenty-sixth day, when the use of alcohol was 
resumed, a decided decrease in the power of adding mani¬ 
fested itself. 

It is difficult to estimate how efficient each of us may 
become in our life work, but one thing is certain, that if 
we use alcohol, we shall lose that perfect control over our 
nervous systems, which enabled the two players to be so 
efficient in the ball game. It is also equally certain that 
if we use alcohol, we shall find fewer men willing to em¬ 
ploy us in places of responsibility, not only because of our 



Figure 420. —• Brain Control. 






478 


THE NERVOUS SYSTEM OF MAN 


mental inefficiency, but also because of our unreliable 
judgment. 

Alcohol Shortens Life. — In 1909 forty-three of the lead¬ 
ing insurance companies in the United States and Canada 
agreed to make an impartial study of all their records for 
the past twenty-five years. This involved an examination 
of 2,000,000 insured lives. The insured were divided into 
many classes, such as railroading, mining, manufacturing, 
and users of alcoholic liquors. The two following statements 
are made by Arthur Hunter, the chairman of the committee, 
in a study covering a period of three and one half years. 

“Liquor Business ; — There is a general impression that saloon 
keepers do not live as long as persons in non-hazardous occupations, 
but it is not generally known that most classes which are connected 
with either the manufacture or sale of liquor have a high mortality. 
Among saloon proprietors, whether they attended the bar or not, there 
was an extra mortality of 70 per cent; and the causes of death in¬ 
dicated that a free use of alcoholic beverages had caused many of the 
deaths. The hotel proprietors who attended the bar either occasionally 
or regularly had as high a mortality as the saloon keepers, i.e., the life¬ 
time was reduced about six years on the average on account of their 
occupation. The mortality among those connected with breweries 
was about one third above the normal. The large class of proprietors 
of wholesale liquor houses had an extra mortality of about one fifth. 
In the fourteen subdivisions of the trades connected with the manu¬ 
facture or sale of alcohol, there was only one class which had a normal 
mortality, and that was the distillery proprietors. The facts regarding 
the adverse effect on longevity of engaging in the liquor trade are such 
that, if they were generally known, young men who are easily tempted 
would be deterred from entering this business. 

Habits as to Alcoholic Beverages. — Nothing has been more con¬ 
clusively proved than that a steady, free use of alcoholic beverages, 
or occasional excesses, are detrimental to the individual. In my 
judgment, it has also been proved beyond peradventure of doubt that 
total abstinence from alcohol is of value to humanity; it is certain that 
abstainers live longer than persons who use alcoholic beverages. The 
low mortality among abstainers may not be due solely to abstinence 
from alcohol, but to abstinence from tobacco, and to a careful regard 
for one’s physical well-being. 


ALCOHOL, A NARCOTIC 


479 


Among the men who admitted that they had taken alcohol oc¬ 
casionally to excess in the past, but whose habits were considered 
satisfactory when they were insured, there were 289 deaths, while 
there would have been only 190 deaths had this group been friade up 
of insured lives in general. The extra mortality was, therefore, over 
50 per cent, which was equivalent to a reduction of over four years in 
the average life of these men. If this meant that four years would 
be cut off the end of the average normal lifetime of each man, there 
are many who would consider that ‘ the game was worth the candle ’; 
but it means that in each year a number of men will die at an earlier 
age than they should. For example, at age 35, the expectation of life 
is 32 years: in the first year after that age, instead of, say, 9 persons 
dying, there would probably be 12 deaths; that is, three men would 
each lose 32 years of life; in the next year probably four men would 
each lose 31 years of life, etc. As a matter of fact, many immoderate 
drinkers would live longer than 32 years, but not nearly so many as 
would live if they had been moderate drinkers, and far fewer than if 
they had been total abstainers from alcohol.” 

366. Alcohol, a Narcotic. — Before studying this subject 
further we must understand the meaning of the terms 
poison, anesthetic (an-es-thet'ik), and narcotic. A poison 
is a substance which when taken into the body tends to .cause 
death. Aconite, opium, carbolic acid, and mercury are all 
poisons, and when taken in sufficient quantities cause death. 

An anesthetic is a substance like ether or chloroform, 
which when breathed into the lungs causes a temporary 
loss of sensation. Unless anesthetics are administered 
properly, they may cause death. 

A narcotic is a substance which causes dullness or stupor, 
and even a temporary relief from pain. 

To understand how alcohol comes to be classed as a 
narcotic, it is necessary to learn about a substance called 
lipoid (lip'oid : Greek, lipos , fat; eikos, like); and as you 
read about this substance in protoplasm, you will realize that 
the charges against alcohol have a real scientific basis. 

“Within recent years a new sort of body substance has been dis¬ 
covered, and has been elevated to first-rate importance. This new 


480 


THE NERVOUS SYSTEM OF MAN 


class is termed ‘lipoid.’ Its importance is immense. It is quite as 
important in the body as the nitrogenous or albuminous material 
which is present in every living tissue. It is very like fat in many 
respects,' but in other respects it is different. It contains nitrogen, 
which fats do not; it contains phosphorus, which fats do not; again 
it mixes with water, which, as is well known, fats do not. It has 
certain remarkable properties, in that it can make certain bodies 
soluble which are otherwise not soluble. 

“The walls of practically every living cell in the whole body are 
made chiefly of lipoid, and it is found that there are strands of this 
material running through and through the substance of every cell. 
In fact, there is no region of any cell in any part of the body that is 
without this material. 

“Perhaps the largest accumulation of lipoid is that in the nervous 
system. There is far more lipoid in the brain than in any other tissue. 
If you examine a nerve, or what physiologists call a nerve trunk, you 
will find that this nerve is composed of many thousands of nerve fibers, 
and each nerve fiber that conveys messages into or out of the brain is 
invested with an insulation jacket (similar to the insulation covering 
an electric wire) of lipoid and thus the stimuli are prevented from 
scattering. 

“It may be asked, ‘What has all this to do with alcohol?’ The 
connection is an important one, for only a few years ago two physio¬ 
logical investigators, — one with the English name of Overton, and the 
other with the distinctly German name of Hans Meyer, — without 
knowledge of each other’s work, discovered the principle that any 
substance that dissolved lipoid, or, what is the same thing, is dissolved 
in lipoid, is an anesthetic. Chloroform, ether, and all of these agents 
which are used in modern surgery to produce unconsciousness are 
dissolvers of lipoid. 

“Besides acting as anesthetics such substances act as poisons to 
every living thing in the body as well. The brain, owing to its high 
percentage of lipoid, is more sensitive to the action of chloroform than 
other organs of the body. 

“When chemists and physiologists found that lipoid was soluble in 
alcohol, it enabled them to rank alcohol as a narcotic poison, and it is 
now so classed. This statement is altogether irrespective of the effects 
it will produce on an animal.” Osborne. 

The question of brain efficiency is further illustrated by 
Figure 420. Long before birth the heart in the embryo 
begins to beat and is under the control of the nervous system. 


STRUCTURAL CHANGES DUE TO ALCOHOL 481 


The part of the brain which superintends the heart is located 
in the medulla, where a special cluster of cells sends out 
nerve fibers which enter the heart nerve. These nerve cells 
are called the heart center. 

The next nerve center to begin work is the breathing 
center, located close to the heart center, which controls the 
breathing. This does not become active until after birth. 

About a year after birth, several more nerve centers be¬ 
come active in the child’s brain. These are the ones which 
help him to walk. The cerebellum contains nerve centers 
which play an important part in walking and in learning to 
balance. The muscles which move the arms and legs are 
regulated by nerve centers in the cerebrum. 

Soon after the child learns to walk, he begins to talk and 
learn words. The several nerve centers which now become 
active are all located in the cerebrum. These are the nerve 
cells which are necessary in speaking, hearing, reading, and 
writing words. 

After the age of fifteen years the brain goes through impor¬ 
tant structural changes and the young person begins to do 
hard tasks well. It is difficult to locate the exact spots in the 
cerebrum where the nerve centers are that now become 
active, for they are widely distributed. These nerve centers 
may be called the efficiency centers and they are the last to 
develop. But as they become active, every one becomes skill¬ 
ful in respect to some one thing, although many years of train¬ 
ing are necessary before the maximum of efficiency is reached. 

The efficiency centers which are the last to become active 
and which require so much energy to train properly are the 
first to be affected by alcohol. 

367. Structural Changes Due to Alcohol. — Definite 
changes are found in the protoplasm of nerve cells after the 
use of alcohol. These consist in a shrinking of the nucleus, 
the loss of the spindle-shaped (Nissl) bodies (Figure 414), 
the swelling of the cell, and the presence of vacuoles in the 


482 


THE NERVOUS SYSTEM OF MAN 


cytoplasm. It is also probable that some of the nerve cells 
are actually destroyed. These physical changes explain 
why the results are so great and why complete recovery of 
mental efficiency in the drunkard is so doubtful. The 
modern point of view and the one which is becoming firmly 
established in the treatment of drunkards by physicians 
is that alcoholism is a disease. 

Anything which can destroy all the higher and finer 
emotions, take away ambition, destroy shame, modesty, 
pride in personal appearance, render one especially liable 
to common diseases, or lead unerringly to insanity is to be 
avoided by all. 

368. Tobacco. — “ Training starts to-morrow, no more 
smoking/’ is part of the athletic coach’s orders at the begin¬ 
ning of each season. He knows that the boy who smokes 
cannot reach his highest efficiency or be relied upon at critical 
times in the contest. He would rather have boys who do 
not smoke, because they are stronger, larger, and steadier 
than those who smoke. The cigarette habit has spread 
until it threatens the health of thousands of boys of America 
to-day. How is it known that their health is not good? 

. The charts on “ smoker’s heart ” prove this point. 

369. How the Smoker’s Heart Is Affected. — The follow¬ 
ing illustrations on the rate of the heart beat and the 
strength of the pulse, by W. A. McKeever, for thirteen 
years professor of philosophy in Kansas University, show 
what really happens when we smoke. There is much in 
these illustrations to warrant the conclusion that the 
heart of the habitual cigarette smoker is weak and feeble, 
except for the few minutes during which he is indulging 
the habit, and that the pulsations at this time are un¬ 
duly excited. Figure 421 shows three records of a young 
man nineteen years old who began smoking cigarettes 
at the age of fifteen and who inhaled the fumes. The 
three records were taken without removing or readjusting 


HOW THE SMOKER’S HEART IS AFFECTED 483 


the instrument, as follows : No. I, immediately before smok¬ 
ing; No. II, during the indulgence of the habit, and No. 
HI, fifteen minutes later, after the effect of the narcotic 
had become apparent. 

Now, by reference to Fig¬ 
ure 422, No. Ill, we may 
observe how this young 
man’s heart should record 
itself, for the latter is the 
tracing of the heart pulsa¬ 
tions of a normal young 
man of the same age and 
temperament. Nos. IV to 
VI (Figure 421) are repre¬ 
sentative of another in¬ 
haler twenty years old, 
who began the practice at thirteen. He now uses a strong 
pipe. 

In Figure 422, Nos. I and II, taken respectively before 
and after smoking, are tracings of a sensitive youth of eight¬ 
een who has been smok¬ 
ing only two years. Ob¬ 
serve the skip of his heart 
beat at x and the cor¬ 
responding partial skip 
under the stimulus of 
smoking in No. II. No. 
Ill (Figure 422), as men¬ 
tioned above, is a trac¬ 
ing of a strong healthy 
heart of a young man of 
somewhat excitable tem¬ 
perament. No. IV represents the phlegmatic temperament, 
that is, a person who is not excitable. No. V is the heart 
tracing of a strong and healthy young woman. 






484 


THE NERVOUS SYSTEM OF MAN 


In Figure 423, Nos. I and II are the pulse records of a man 
of splendid physique, thirty-six years old and weighing 230 
pounds. No. I was taken before and No. II after smoking 
a cigar. He does not inhale. His pulse responded readily 
to the stimulus, but as the first tracing indicates he does not 
seem -to suffer from any heart prostrations between indul¬ 
gences. No. Ill is the record of a person whose vitality 
is temporarily low from nervous fatigue. No. IV is the 
record of a young woman who was on the verge of nervous 

prostration. No. V is 
representative of a heart 
weakened by long indul¬ 
gence in the smoking 
habit. The young man 
in question began early 
and continued the prac¬ 
tice till his physician con¬ 
vinced him of the extreme 
danger threatening his 
life. The pulse wave is 
nearly normal in length, 
but is entirely too weak. Under such conditions of heart 
action a man is capable of little courage or aggressiveness. 

Says Mr. McKeever: 

‘‘From the foregoing evidence we are led to the conclusion, that in 
the case of boys and youths, cigarette smoking is very deleterious to 
the physical and mental well-being. Moreover, my investigations 
indicate that it makes very little difference in the effects whether the 
victim uses pipe or cigarettes, provided he inhales the fumes; and 
with few exceptions the young smokers are inhalers. The ordinary 
case exhibits about the following type of conduct: (1) While the crav¬ 
ing is at its height the victim manifests much uneasiness and often much 
excitation. (2) During the indulgence the cheek is alternately flushed 
and blanched, the respiration considerably increased, and the hands 
tremble. (3) About twenty minutes after smoking the muscles become 
relaxed, the respiration slow and shallow, the skin on the face dry and 
sallow, and there is an apparent feeling of unconcern about everything.” 




SMOKING AND SCHOLARSHIP 


485 


370. Smoking and Scholarship. — Several thousand boys 
have been studied and classified according to age and whether 
they were smokers or non-smokers. In all cases the non- 
smokers had a higher average grade of scholarship. The 
experience of city superintendents and principals is that they 
can usually tell a cigarette boy by his general attitude, poor 
scholarship, and disregard of personal appearance. 

When cigarettes are burned, three distinct poisons are 
produced, which cause serious effects on the boys who use 
tobacco in this form. These poisons are absorbed in small 
quantities by the mucous membrane which lines the nasal 
passages and in larger quantities when the smoke is inhaled 
in the lungs. 

A simple way to prove that cigarette smoke contains a 
poison is by blowing the smoke through a glass tube into 
an aquarium containing goldfish. Only a small amount of 
smoke will kill the fish. 

While we all can gradually adapt ourselves to small 
amounts of poison, poisons are never beneficial unless pre¬ 
scribed by a physician to try to remedy some bodily defect. 
The poisons which arise from the burning of a cigarette 
are never prescribed even as medicines, and have never 
been found in any way beneficial to the human body. 

SUMMARY 

The nervous system of all vertebrates consists of a brain 
and spinal cord with nerves passing to all organs of the 
body. The brain of man is the most highly developed. 

All our movements are controlled by means of the nervous 
system. Through our sense organs we gain our information 
of the world. 

The nervous system is made up of cells which are highly 
specialized. Their main work is to transmit and interpret 
stimuli. The nerves of man are so highly specialized that 
all stimuli which affect the eye are thought by us to be light 


486 


THE NERVOUS SYSTEM OF MAN 


stimuli; or all stimuli which enter in the ear, seem to be 
sounds. The stimulus which passes over any of our special 
sense organs travels over several different nerve cells before 
it reaches the place in the brain where it is interpreted. The 
highly specialized nervous system and sense organs grow and 
are fed just as muscles or skin grow and are fed. There 
is no special food which we can eat that is used exclusively 
by the nervous system. 

QUESTIONS 

What is the nervous system ? Of what parts is it composed ? 
What animals have you studied that have a nervous system? Which 
ones lack a special nervous system? How does the nervous system 
grow? Describe the nerve cell. How does it differ from other cells 
in man? What are special senses? What kind of information do you 
receive through your eyes ? What kind through your ears ? Which do 
you remember? (The well-trained mind remembers equally well the 
information that comes in through each of his sense organs.) 

REFERENCES 

Cutten, The Psychology of Alcoholism. 

Davenport, Heredity in Relation to Eugenics. 

Guyer, Being Well-born. 

Horsley and Sturge, Alcoholism and the Human Body. 


CHAPTER XXXV 


THE BIOLOGY OF DISEASE 1 

STUDENT REPORT 

How many in the class have been sick during the past year? Of 
how many different diseases? What was done to aid each one in 
getting well? What was done to prevent others from taking the 
same diseases? What was done by your Health officer? (Consult 
the reports of the State Board of Health and of the local health official.) 

371. Disease. — Usually people go through their daily 
occupations without feeling pain or bodily discomfort. 
Such a condition is known as health. Sometimes, how¬ 
ever, they go about their usual duties when they do not 
feel well and the indisposition gradually passes away. But 
in other cases the ill feeling becomes severe, the usual ac¬ 
tivities are given up, and we say that they are sick. Sick¬ 
ness may last for only a short time or for many years. The 
usual conditions of the body are changed, and we say that 
the body is diseased. The apple, the tree, the dog, the 
horse, each has its own diseases. 

372. Cause of Disease. — While there are many causes 
of disease, all of them may be grouped under four headings: 
(1) Inherited diseases, i.e. those transmitted from parent 
to child, as certain forms of insanity and imbecility. (2) Dis¬ 
eases caused by such poisons as lead, arsenic, mercury, phos¬ 
phorus, opium, cocaine, alcohol, and the like. The dis¬ 
turbances which these chemical agents set up in animal 
tissues are easily recognized by a good physician. (3) Dis¬ 
eases which cause certain tissues to take on an abnormal 


1 Chapter XXIII, Bacteria, may be read in connection with this chapter. 

487 



488 


THE BIOLOGY OF DISEASE 


growth, as in tumors and cancers. (4) Diseases caused 
directly or indirectly by some definite living plant or animal. 
Such diseases are called “ biological diseases,” because the 
source or cause is in all instances some definite living plant 
or animal. In our ordinary daily speech we often speak of 
such ills as “ germ ” diseases. 

373. Biological Diseases. — The rattlesnake secretes a 
poison which is forced through fangs or hollow teeth into 
the blood of its prey. This poison affects the heart and 
may result in death. One of the common and beautiful 
mushrooms produces a similar poison which is not de¬ 
stroyed by cooking. If this particular mushroom is eaten, 
death is almost certain to follow in from twenty-four to 
forty-eight hours. In both these cases the animal or plant 
is large enough to be seen and easily recognized. 

But there are a considerable number of microscopic 
plants and a few microscopic animals that have formed 
the habit of living for at least a part of their life in other 
plants and animals. During this time, as we have seen in 
the study of animal and plant parasites, they usually secure 
all, or the greater part, of their food from the plant or animal 
in which they are living. Two general causes of disease 
result from this parasitic habit. The parasite may destroy 
certain cells of the body, or the material thrown off from 
the body of the parasite may act as a specific poison. 

374. Communicable Diseases. — The term communicable 
disease 1 is used in this book to mean the diseases caused by 
a plant or animal living as a parasite in plants, animals, or 


1 New York State designates the following as communicable diseases : 
anthrax; chickenpox; cholera, Asiatic; diphtheria (membranous croup)- 
ysentery, amoebic and bacillary; epidemic cerebro-spinal meningitis; 
epidemic or streptococcus septic sore throat; German measles ; glanders • 
measles ; mumps ; ophthalmia neonatorum ; para-typhoid fever ; plague • 
poliomyelitis acute anterior (infantile paralysis); puerperal septicaemia;’ 
rabies , scarlet fever ; smallpox ; trachoma ; tuberculosis ; typhoid fever • 
typhus fever; whooping cough. 




Professor Theobald Smith (1859-still living) is a technical 
scientist. Before any physician knew how to prevent disease, 
technical biologists had to discover how the disease germs live. 
Such is the work of Professor Smith, and he is an acknowledged 
authority in his field 

His best known discoveries are as follows: 1. He discovered 
that the protozoan parasite in the blood of cattle which causes 
Texas cattle fever is also found in ticks. It is carried from one 
cow to another by the infected ticks. This discovery led to simi¬ 
lar discoveries in Malaria, Sleeping Sickness, and other protozoan 
diseases. 2. His scholarly researches in human tuberculosis 
have been of great value to mankind. 3. Present standards of 
meat inspection are based upon his investigations into the dis¬ 
eases of cattle and other food animals. 4. He was a pioneer in 
the manufacture and 'extensive public use of antitoxin. 






PULMONARY TUBERCULOSIS 


489 


man. These diseases are communicated in various ways 
from one individual to another, from one animal to another, 
or from one plant to another. 

The following are among the most common communi¬ 
cable diseases. Diseases caused by bacteria (minute plants) 
are tuberculosis, pneumonia, diphtheria, typhoid fever, 
bubonic plague, and whooping cough. Measles and scarlet 
fever are so similar to these in many ways that it is believed 
that they are caused by bacteria, although the definite 
bacteria which cause them have not been discovered. Dis¬ 
eases caused by protozoa (minute animals) are malaria, 
yellow fever, sleeping sickness, possibly smallpox, and others 
less well known. 

The biological diseases are all preventable, especially 
the communicable diseases which result from the parasitic 
habit of some plant or animal. In order to prevent these 
diseases, it is necessary to know how the different plants 
and animals gain access to the human body and proceed 
to live there. This can be illustrated by describing pul¬ 
monary tuberculosis, a plant or bacterial disease; and 
malaria, an animal or protozoan disease. 

375. Pulmonary Tuberculosis. — Pulmonary tuberculosis 
is a disease located in the lungs. The cause is a definite 
plant with parts and habits which are easily recognized by 
bacteriologists (students of bacteria). This plant is called 
Bacillus tuberculosis , and was proved to be the cause of 
consumption, or tuberculosis, by Robert Koch, a German 
scientist, in 1882. These tuberculosis bacteria, or germs, 
in countless numbers are found leading a parasitic life in 
the lungs of a tubercular patient. The bacteria are ex¬ 
tremely minute, and can be seen only by the use of a micro¬ 
scope of high power. 

The large number of germs in the lungs grow rapidly 
and they are set free in the air by coughing. One tuber¬ 
culosis patient may give off millions of these germs in a 


490 


THE BIOLOGY OF DISEASE 


day. For this reason great care should be taken in destroy¬ 
ing the sputum of patients, for if the germs become dry, 
they are carried about as dust particles. 

Tuberculosis and other disease germs are so numerous 
that it is impossible to escape taking some of them into our 
bodies, but they usually do us no harm unless we are in a 
weakened condition. 

Modern methods of cleaning the streets by flushing with 
water, keeping garbage covered, and wiping up the dust 



Figure 424. — Tuberculosis Cure, Summer. 


in our homes instead of using the old-fashioned feather 
duster are doing much to keep down the number of germs 
in the air which we breathe. 

The bacteria that are breathed in from the air may find 
some weak place in the lungs in which to take up their 
parasitic lives. Those which enter on the food pass from 
the digestive tract into the blood and are eventually carried 
to the lungs. The introduction of tuberculosis germs in 





GETTING WELL 


491 


this way is especially frequent in children. In many cases 
milk from the tuberculous cows is the source of the germs. 

The cause of pulmonary tuberculosis is, then, the tubercle 
bacillus, which is taken into the lungs in the air we breathe, 
or through the food eaten, or by personal contact with a 
consumptive patient. These germs cause certain parts of 
the lungs to become diseased. 

376. Getting Well. — Consumption is not necessarily 
fatal, especially if treated in its earliest stages. But many 



Figure 425. — Tuberculosis Cure, Winter. 


people who have the disease do not consult a regular phy¬ 
sician until it has made considerable progress, and then it 
is too late to bring about a cure. 

Figures 424 and 425 show the present method used in 
treating tuberculosis. The patients are given tissue-build¬ 
ing food (protein) and are required to sit and sleep out- 
of-doors as much as possible. Rest, good food, and fresh 
air work wonders in arresting the progress of this disease. 













492 


THE BIOLOGY OF DISEASE 


When the body gains the requisite amount of strength 
the disease and its germs are usually thrown off. Patent 
medicines and alcohol should be avoided, as they reduce 
the power of the body to resist disease and give no aid in 
building up the diseased tissues. In addition, alcohol causes 
serious disturbances in the general circulation. 

In addition to pulmonary tuberculosis physicians recog¬ 
nize tuberculosis of the throat, intestines, kidneys, brain, 
and joints. 

377. Influenza. — This is a communicable disease that 
killed more than 550,000 people in the United States during 
the fall of 1918 and the winter of 1919, which is about five 
times the number (111,179) of American soldiers officially 
stated to have lost their lives from all causes in the World 
War up to the date of April 30, 1919. This disease is con¬ 
tracted only by those who come in contact with the secretions 
from the nose or bronchial tubes of one who is affected with it. 
The word contagious is properly used for such diseases, because 
the person suffering from them gives off germs that pass to 
another. In this same sense tuberculosis, diphtheria, and 
typhoid fever are contagious diseases. 

When the disease is of average severity the symptoms are 
a chilly sensation, headache, and “ bone ache,” or pains all 
over the body, and fever. Coughs usually develop as the 
progress of the inflammation extends into the bronchial tubes. 
The full force of this disease may center in the respiratory 
organs, or in the muscles and nerves, or in the digestive 
tract. It is clear that influenza paves the way for pneu¬ 
monia, if it does not actually produce it. 

The mouth and nasal passages should be kept clean with 
such washes as salt in water or borax in water in the pro¬ 
portion of one level teaspoonful to a pint of water. The 
chief value of all nasal washes is the water, and any prepara¬ 
tion that has a smarting reaction should be avoided. There 
is really no special method of cleaning the nose that excels 


SOURCE OF THE MALARIAL PARASITE 493 


the natural method, i.e. blow it, and blow it into a paper 
napkin and burn the napkin. 

This disease spreads in epidemic form about once in a 
generation throughout the earth along the routes of travel, 
and is carried from place to place by man. The name 
Influenza was given to it in Italy about one hundred years 
ago, because it was supposed to be due to the influence of 
some malevolent agent of the air. The French term “ La 
Grippe ” is given to this same disease; while the expression 
Spanish Influenza simply means that the 1918 epidemic 
started in Spain or was first noticed in epidemic form in Spain. 

Home Report. — Look up the ravages of influenza in India, 
Alaska, etc. 1 See what you ckn find out about the total 
number of deaths in the different nations of the world. 

378. Malaria. A Protozoan Disease. — Malaria is a 
disease caused by a protozoan or minute animal which is 
distributed over the greater part of the world.. The ma¬ 
laria protozoon is a minute simple cell of living matter. It 
resembles the amoeba in its form and ability to change. 
This parasite penetrates into the red blood corpuscles and 
remains in them for twenty-four or forty-eight hours, or 
until the substance of the corpuscle is nearly used up. Then 
the parasite escapes into the plasma of the blood and later 
enters a fresh corpuscle. 

379. Source of the Malarial Parasite. — The word ma¬ 
laria means bad air, for it was former^ believed that foul 
air caused the disease. When it was learned that a definite 
animal was the cause both in man and in other animals, the 
problem was to find how the parasite entered the body. It 
has been proved to the satisfaction of scientists that the 
malarial protozoon is injected into the blood by a particular 
kind of mosquito (Anopheles) which carries malaria germs 
in its body. (See page 55.) 

1 Influenza Studies by Raymond Pearl. Reprint No. 548, Public Health 
Reports, Treasury Department. 



494 


THE BIOLOGY OF DISEASE 


The mosquito sucks the blood from a man or an animal 
suffering from malaria. This blood contains some of the 
malarial parasites, which pass into the stomach of the mos¬ 
quito. They then migrate into the salivary glands of the 
mosquito, so that as soon as the mosquito bites another 
man or animal, it pours out some saliva which introduces 
the parasites into the victim’s blood. While in the body 
of the mosquito, these parasites pass through definite stages 
in their life history; and when they reach the blood of man, 
the remaining stages are completed. Thus a man, or an 
animal, and a particular mosquito are necessary for the 
complete life history of the malarial parasite. 

This means in addition that for the prevention of malaria 
all that is necessary is to prevent the Anopheles mosquito 
from breeding, or in case this cannot be done, to screen ade¬ 
quately the houses, tents, and bedrooms in the regions where 
the mosquitoes live. It is interesting to note that the 
methods for the prevention of malaria were more than 
anything else responsible for the successful completion of 
the Panama Canal. The construction of this important work 
thus became a health as well as an engineering problem. 

380. Other Protozoan Diseases. — Other protozoan dis¬ 
eases are produced in the same manner as malaria. The 
carrier may be different, but the principle of spreading the 
diseases is the same. Yellow fever, for instance, is spread 
by another kind of mosquito, and sleeping sickness by the 
tsetse (tset'se) fly. (See page 55.) 

381. Hookworm Disease. — This disease is caused by a 
parasite which is classified as one of the worms. Hook¬ 
worm disease belts the earth in a zone which extends thirty- 
three degrees each side of the equator. Great progress is 
being made in the United States in curing those suffering 
from this disease. The wearing of shoes and the use of a 
sanitary closet are usually sufficient preventives to protect 
the people who live in a hookworm district. 


QUESTIONS 


495 


The worms that cause trichinosis are closely related to hook¬ 
worms. This disease is due to the round-worm, trichinella, 
and comes from eating partly cooked pork that has these 
worms in the flesh. This is becoming a rare disease, due to 
the painstaking inspection of slaughter-houses by the gov¬ 
ernment. Flat tapeworms are often found in dogs, cats, 
and fish. Occasionally one gains access to the intestinal 
tract of man. Here it rapidly grows into the adult stage, 
living upon the food that should go to nourish man. 

SUMMARY 

Disease prevents us from working as we do when we are 
well. Most diseases are unnecessary and preventable, es¬ 
pecially those which are caused by plants or animals living 
as parasites in our bodies. In most of the biological diseases 
some definite poison produced by the parasite is taken into 
the body, and this is the chief cause of disease. Tuber¬ 
culosis, the “ great white plague,” is caused by a plant 
named bacillus tuberculosis and often referred to by phy¬ 
sicians as “ Tb.” One can get well if the body is able to 
overcome the poisons secreted by these minute plants. 
Each disease caused by bacteria has its own special history 
and the symptoms of the disease are definite and distinct. 
Influenza is probably a germ disease, but the exact kind of 
bacteria is still unknown. It was epidemic over nearly the 
whole world in 1918 and 1919. Malaria is a disease due to 
a protozoan parasite living in the blood corpuscles of man. 
These parasites are introduced into the blood through the 
bite of Anopheles mosquitoes. 

QUESTIONS 

What are the biological diseases ? How are these diseases caused ? 
How many kinds of tuberculosis are there? Is diphtheria a germ 
disease? Are colds germ diseases? Describe malaria. What effect 
has malaria had upon the settlement of our country? This is a home 
study question. 


496 


THE BIOLOGY OF DISEASE 


REFERENCES 

Celli-Eyre, Malaria. 

Chalmers, The Beloved Physician Edward L. Trudeau. 

Knoff, Tuberculosis, A Preventable and Curable Disease. 

Stiles, Prevalence and Geographical Distribution of Hookworm 
Disease. Hygienic Laboratory, Bulletin Number 10, Washington. 
Trudeau, Edward L., An Autobiography. 


CHAPTER XXXVI 


PREVENTION OF DISEASE 

382. Preventable Disease. — More than 600,000 lives 
and more than a million dollars are wasted in the United 
States each year by preventable disease. For this careless¬ 
ness and ignorance are chiefly responsible. Preventable 
disease can be practically wiped out by vigilance, cleanliness, 
and wholesome living, in short, by sanitation. 

Prevention of Communicable Diseases. — The prevention 
of these diseases depends upon an understanding of the causes 
which produce them, close adherence to the laws of hygiene, 
and especially the exercising of proper care in the produc¬ 
tion and cooking of our food. Germ diseases are unneces¬ 
sary, and it should be considered a disgrace to a community 
if some of them appear. 

Proper hygienic measures will do much towards eliminating 
most of the communicable diseases, but until the intelligence 
of communities can be aroused enough so that such measures 
shall be insisted upon, we must depend upon proper food, 
rest, fresh air, and exercise to keep ourselves fit, and thus 
avoid the conditions which help disease to gain a foothold. 
Tuberculosis, for example, is more likely to occur in persons 
who are underfed and overworked, and a cold often follows 
an attack of indigestion. 

Care of Food. — The care of food is extremely necessary 
in preserving our bodily well-being, for the same germs 
live and grow in food which cause disease when taken into 
our bodies. One method of keeping the bacteria on food 
from growing is by proper refrigeration. The temperature 

497 


498 


PREVENTION OF DISEASE 


of a well-cooled refrigerator does not destroy the germs, but 
makes them incapable of growth until heat is supplied them. 
If food is taken from the refrigerator and allowed to stand 
for a time, the bacteria will at once begin to grow and cause 
the food to spoil. If such food is eaten, an intestinal dis¬ 
turbance usually results. 

In the attempts to prevent disease, more study has been 
given to milk and water than to other necessities. For 
discussion of milk, see pages 313-315. 

While milk is used as a food by all mankind, water is 
even more important, for it is absolutely necessary if we 

are to continue to live. 
In this respect man is like 
all plants and all other 
animalis, water being 
necessary for the preser¬ 
vation of all life. 

Two conditions must be 
met before a water supply 
can be deemed satisfac¬ 
tory. There must be an 
abundant supply; but 
more important still, the 
water must be pure, that 
is, free from disease-pro¬ 
ducing germs. Farmers 
and residents of small towns may without great trouble secure 
sufficient pure water, but the large cities have to spend 
millions of dollars in providing an adequate water supply. 

Sanitary measures are adopted to keep the sources of 
the water from becoming impure, as well as to keep clean 
the reservoir where it is stored. Certain harmless plants 
and animals living in reservoirs may give an unpleasant 
taste or odor to the water. Harmful disease germs live 
in water for months. Such germs may be frozen in ice, 



Figure 426. — Milk Diluted to 


Left-hand culture from clean milk; 
right-hand culture from dirty milk. 
Count the number of spots in each 
plate and multiply by 1000 and you will 
have some idea of the difference be¬ 
tween clean and dirty milk. Certified 
milk is almost free from bacteria. 



KEEPING WELL 


499 


stored in ice houses, and when later put with the ice into 
drinking water, may cause typhoid fever. It is, therefore, 
important that we have plenty of pure water, and we should 
do all we can to help in giving the town or city in which we 
live a pure water supply. 

STUDENT REPORT 

Prepare a report on the water supply in your locality and find where 
it comes from. What measures are taken to keep the sources and res¬ 
ervoir clean? 

383. Keeping Well. — Our best doctors are spending 
much effort in showing how to avoid disease, for no one is 
benefited by illness. The old notion, that children should 
IF 

THESE CASES THESE CASES 



The Story of the Epidehtc of Septic Sore Throat at Rockville Centre, L. I. 


Figure 427. 

be exposed to measles, scarlet fever, and whooping cough 
is wrong, for none of these childhood diseases is necessary. 
The time will come when our homes and surroundings will 
be so sanitary that the common diseases caused by germs 
will be eliminated, or at least decreased in number. 





500 


PREVENTION OF DISEASE 


Government inspection of meats is lessening the amount 
of disease contracted from eating diseased pork, other meat, 
and fish. The United States Department of Agriculture is 
making every effort to inspect such products, and the 
department is fairly successful in inspecting the larger 
establishments. Many cattle and hogs, however, are killed 
and sold locally and they escape inspection, so that buyers 



Figure 428. — Malarial Swamp. 

An ideal place for mosquitoes to breed. 


of this meat have no protection against a general condition 
of disease. 

Another danger to health is from the people known as 
“ carriers ” of disease, as such people give no evidences of 
illness. Typhoid and diphtheria are the two diseases 
most likely to be carried in this way. Many of these carriers 
serve as cooks, and as they give no evidence of being in 
other than perfect health, they often spread the germs 
through the food they prepare. If habits of absolute clean¬ 
liness are insisted upon, much of the danger of the dissemi¬ 
nation of germs in this way may be removed. 




QUACKS AND PARENT MEDICINES 501 

Many hotels, public institutions, and well-run house¬ 
holds insist that a prospective servant shall be examined 
by a competent physician before being engaged for work. 
In this way carriers may be detected, and persons with 
germ diseases, like tuberculosis, for instance, are prevented 
from spreading disease either in the food or in the air. 

Children in the schools frequently, have diphtheria germs 
living in their nasal passages or throats, but are not ill. 
After a time a number of children are stricken with the dis¬ 
ease. A doctor then takes a sample of the contents of the 
throat and nose of each child. The bacteria in the mucus 
from the nasal passages- are allowed to grow for twenty-four 
hours in a special preparation called a culture (page 312). 
At the end of that period the cultures are stained and ex¬ 
amined with a high power microscope, and if diphtheria germs 
are present, they are easily seen. If one of the well children 
has these germs, he is treated until they disappear. 

384. Quacks and Patent Medicines. — The term quack is 
applied to a person who pretends to skill or knowledge which 
he does not possess. Technically, a patent medicine is a 
medicine whose composition is a matter of public record, and 
for which letters-patent have been granted which give 
the patentee the exclusive right to the manufacture and 
sale of this product for seventeen years. Colloquially, 
however, a “ patent medicine ” is a remedy, usually secret 
in composition, to which a fancy name has been given and 
that name trade-marked. Such a trade-mark gives to the 
owner a perpetual monopoly on the name while it imposes no 
restrictions on the composition of the product that goes 
under that name. Most so-called patent medicines are of 
the latter type and are really not patented at all. Many 
millions of dollars are spent annually in advertising special 
“ cures ” and mechanical contrivances guaranteed to cure 
diseases for which they can do nothing, or even to cure such 
diseases as cancer, tuberculosis, epilepsy, etc. 


502 


PREVENTION OF DISEASE 



Many people who do not understand the causes of dis¬ 
ease are reluctant to consult a well-trained physician, but 
read and believe the carefully worded advertisement of 
some quack doctor or of some patent medicine. The 
untrained sufferer cannot interpret the meaning of his 
distress and is incompetent to select the proper medicine. 


Figure 429. — X-ray of the Foot of a Girl Wearing a High Heel Shoe. 

The many layers of leather in the heel were fastened by means of glue. 
Notice the effect of raising the heel so high. It weakens the muscles on 
the back of the heel and places an unusual strain on the muscles of the 
arch of the foot. The wearing of such shoes is the source of much discom¬ 
fort and is just one illustration of what one should not do who wishes to 
keep well. Compare with Figure 430. 

As real medicine is given for specific symptoms associated 
with a specific disease, it is apparent that a patent medi¬ 
cine advertised to cure from six to forty diseases is worth¬ 
less. Furthermore, real medicine is given to relieve a 
certain set of symptoms at a given stage of the disease, 
and is frequently changed. This is, of course, impossible 
when using a patent medicine. If every one would consult 




QUACKS AND PATENT MEDICINES 


503 


regular physicians, and cease patronizing the quacks and 
patent medicines, one of the sources of much sickness and 
suffering would be destroyed. 

Our government through its enforcement of the Food and 
Drugs Act is doing a great deal to protect those who do not 
understand about disease and its cure. This Act is too 
limited and should be revised and its scope broadened; for 



Note how differently the pressure comes on the parts of this foot as 
compared with that shown in Figure 429. 

we find since its passage that there has been an increase in 
the number of remedies sold as “ curesfor epilepsy. The 
main drug in these fakes is bromide of potassium, which is 
harmful to the patient, especially in the large doses recom¬ 
mended. While this drug has the power to suppress tem¬ 
porarily the epileptic attack, it leaves the sufferer in a worse 
condition. 

The number of “ deafness cures ” is legion. The middle 
and inner ear, where all diseases of the ear are located, is 
separated from the brain by a thin partition of bone and it 




504 


PREVENTION OF DISEASE 


is extremely dangerous to permit quacks to tamper with such 
a delicate organ as the ear. At the present stage of our scien¬ 
tific information, very little can be done to cure deafness. By 
writing to the American Medical Association, Chicago, Ill., you 
can secure much information about alleged cures for deafness 
as well as about patent medicines and mechanical contrivances. 

Woman’s fashions during the past few years gave a won¬ 
derful stimulus to the exploiters of “ obesity cures.” The 
desire to be slender — often far beyond what is compatible 
with good health — caused thousands of women to waste 
their money on so-called reduction treatments that were 
either dangerous or worthless or both. 

Thyroid extract was the basis of many of the “ fat reduc¬ 
ers ” first put on the market, and this drug is still somewhat 
in use. We are all beginning to realize that this is a danger¬ 
ous drug, so that other things have had to be substituted. 
A very common sea-algae, the kelp (Fucus vesiculosus), 
has been used in many of the fat-reducing preparations. 
It is difficult to find out why this plant is so popular because 
in some localities farmers have used it as food for their hogs 
in the belief that it makes them fat. Overeating and too little 
exercise are the chief causes of obesity. Remove the causes 
and stop buying fakes. 

Between the ages of twelve and eighteen usually, nearly 
all children have pimples, especially on the face. There 
is no remedy that will prevent them. The same can be 
said about the tendency of those of light complexion to 
sun-burn or freckle, only here there is no age limit. Cater¬ 
ing to the ignorance and pride of girls especially, fakers 
advertise numerous cosmetic preparations for the skin, hair, 
etc. Many of these have been analyzed by the chemists 
of the government and found to consist of borax, starch, 
epsom salts, soap, and other common substances which 
cost from one to three cents a bottle and for which the 
user pays fifty cents a bottle. 


QUACKS AND PATENT MEDICINES 


505 


Testimonial letters stating that the writer has been greatly 
benefited by a given patented preparation or mechanical con¬ 
trivance are abundantly used by all fakers. An official of 
the United States Postoffice once wrote: “ Speaking gen¬ 
erally it may be said that in all my experience in this office 
never has a medical concern, no matter how fraudulent its 
methods or worthless its treatment, been unable to produce 
an almost unlimited number of these so-called testimonial 
letters.” An investigation by the American Medical Asso¬ 
ciation has shown that some of these letters are purchased, 
some written in the office of the “ patent medicine ” concern, 
and some actually written in good faith. Those who write 
the letters in good faith are relatively few in number and 
nearly always ignorant and unable to judge accurately of the 
cause of their trouble. Many of them after writing of the 
benefits are found to be just as deaf or epileptic as before tak¬ 
ing. In the case of consumptives who write of being helped, 
it is only necessary to wait a few months and the death certifi¬ 
cates are available as silent testimonial to the fake. 

As the United States Government has been more and more 
successful in prosecuting the ordinary frauds, the propa¬ 
gators of fakes have become more skillful, especially in the 
false-scientific manner of advertising. 

The following is from “ The Nostrum and the Public 
Health ,” an article published in the Journal of the American 
Medical Association, May 24, 1919, written by Arthur J. 
Cramp, M.D.: 

“ The physician, of course, is opposed to the average 
‘ patent medicine ’ because it is exploited in such a way as to 
cause the public to magnify its trivial ailments, to drug 
itself , unnecessarily and in cases in which something serious 
is the matter to lose vitally valuable time in seeking medical 
aid. . . . 

“ Unfortunately, the home remedies of to-day are, generally 
speaking, ‘ patent medicines 1 ; and the methods of promoting 


506 


PREVENTION OF DISEASE 


the sale of patent medicines make those products a menace 
to the public health. This not altogether for what the 
remedies themselves contain, although in many instances 
that is distinctly bad, but because of the way such products 
are exploited. ... So to advertise as to make well men 
think they are sick and sick men think they are very sick, 
for the sole and only purpose of causing them to purchase 
drugs to pour down their throats, is more than an economic 
offense ; it is a crime against the public health. Yet this is 
the principle on which the average ‘ patent medicine ’ 
of to-day is sold.” 

Students of even such an elementary course of biology 
as this, possess the needed information to enable them to 
tell the difference between fakes and real remedies. This 
is one of the important results that you should obtain from 
this study. Learn to seek for the real cause of disease and 
be certain that the results which follow are due to the medi¬ 
cines taken before writing testimonials for fake cures. 

385. Alcohol in Patent Medicine. — Many patent 
medicines contain a considerable amount of. alcohol. Since 
the passage of the national Food and Drugs Act, which went 
into effect January, 1907, the presence and quantity of 
alcohol in “ patent medicines ” has to be declared on the 
label. This alone tended to reduce the amount of alcohol 
in many of them but there still remained a large number of 
preparations whose most active and powerful drug was 
alcohol. Some of these were so slightly medicated that the 
United States Government would not permit them to be 
sold except under a liquor license. Since the advent of 
prohibition, of course, these can be sold only under the 
strict regulations governing the prescribing of alcohol. 

Some patent preparations contain also cocaine or opium 
and should not be taken for this reason. 

386. Alcohol and Disease. — It is unnecessary to make an 
elaborate series of quotations from eminent men to prove 


BOARDS OF HEALTH 


507 


that alcohol is not useful and necessary as a medicine in 
the cure of disease. One of the chief reasons has already 
been given in connection with the discussion of tubercu¬ 
losis. There is no evidence that alcohol has any effect on 
the destructive course of a disease, or any beneficial effect 
upon the person suffering from disease. This last phase 
of the problem has been under critical study long enough 
to show that the earlier claims of the helpfulness of alcohol 
in disease are not supported by the facts. The reverse is 
true. Alcohol is known to decrease the. power of the body 
to withstand disease and does not assist in destroying the 
poisons which arise in the case of bacterial diseases. At 
present there is no scientific evidence which justifies the use 
of patent medicines, or of alcohol unless definitely prescribed 
by a physician. 

387. Headache and Anti-pain Patent Medicines. — Many 
preparations advertised under these general names are taken 
by persons ignorant of the fact that these medicines generally 
contain harmful drugs. It should be sufficient to know that 
no reputable doctor will ever give any of these preparations 
except in a mild form, and in case of extreme pain. No 
person except a trained physician has a right to prescribe 
drugs ; and he only after a knowledge of the patients symp¬ 
toms. Many of these preparations affect the heart and 
blood, and none of them has any beneficial effect on the real 
cause of the pain. 

388. Boards of Health. — Communities and physicians 
have endeavored to prevent the spread of communicable 
diseases by the formation of boards of health, by quaran¬ 
tine, vaccination against smallpox, immunization against 
typhoid fever, the use of antitoxin in diphtheria, disinfect¬ 
ants and fumigants. 

The term Board of Health is applied to a number of in¬ 
dividuals, appointed or elected by a nation, by a state, or 
by a municipality, to enforce the national, state, city, or town 


508 


PREVENTION OF DISEASE 


health laws and regulations. The local officer of this board 
is a physician, and in some states, New York for example, 
is appointed according to the regulations governing the 
city or town in which he is to serve. The New York state 
law defines his work as follows: 

“ Every such local officer should guard against the intro¬ 
duction of such communicable diseases as are designated 
by the State Department of Health by the exercise of proper 
and vigilant medical inspection and control of all persons 
and things infected with or exposed to such diseases, and 
provide suitable places for the treatment and care of sick 
persons who cannot otherwise be provided for.” 1 

Violation of quarantine and of the various health regu¬ 
lations, such as the pollution of water and improper care 
of refuse and sewage, should be reported to the local health 
officer. In case no satisfactory results are obtained from 
the local health officer, the question may be referred to the 
State Board of Health, which gives prompt and efficient 
attention to all questions concerning the health of the 
people of the state. 

389. Quarantine. — When a person or a group of persons 
is suffering from a communicable disease, or when anyone 
has been exposed to the germs of any such disease, the 
Bdard of Health may place him under quarantine . The 
nature of the quarantine depends on the specific disease 
and the laws of the town or state in which the disease is 
prevalent. 

The New York law on this subject is typical of the best 
state laws on quarantine. It says: 

“ The Board of Health shall prohibit and prevent all 
intercourse and communication with or use of infected 
premises, places, and things; and require, and, if necessary, 

1 The Sanitary Code of the Public Health Council of the State of New 
York defines the health officer s duties in detail and may be had by writing 
to the State Department of Health at Albany. 



VACCINATION 


509 


provide the means for the thorough purification and chang¬ 
ing of the same before general intercourse with the same 
or use thereof shall be allowed.’’ 

This means if an individual is suffering from scarlet fever 
or diphtheria, or some other communicable disease, he shall 
not associate with the general public until he has ceased to 
be a source of infection. His liberty is temporarily re¬ 
stricted by quarantine because he may be the cause of sick¬ 
ness and even death to others by spreading the germs of 
communicable disease. 

It is interesting to know that the more highly civilized 
a nation, state, or city becomes, the more specific and exact¬ 
ing are the quarantine regulations. There is every reason 
to believe that in the near future the present laws of quaran¬ 
tine will be extended. In addition to individuals being 
quarantined in a dwelling, all the inhabitants of a city or 
state may be quarantined in case of severe epidemics; or 
the transportation of stock from one state to another may 
be prohibited in the case of a serious communicable disease 
existing in cattle or sheep. The quarantine laws, for ex¬ 
ample, order from time to time that all dogs in the town or 
county shall be muzzled as a protective measure against 
rabies. 

Immigrants suffering from certain diseases are prohibited 
from landing in the United States. This means that there 
are national as well as state and city quarantine laws. The 
present quarantine laws are the most effective protective 
measures against the spread of disease known to man and 
are the product of a high degree of civilization. 

390. Vaccination. — The success which has attended the 
efforts of man to overcome disease is well illustrated by 
smallpox. For centuries this disease was responsible for 
many deaths throughout the world. It is said to have 
existed in China centuries before Christ. Later it swept 
over Europe again and again. A famous French physician 


510 


PREVENTION OF DISEASE 


wrote in 1754 that every tenth death was due to smallpox, 
and that one fourth of mankind was either killed by it or 
disfigured for life. Smallpox was brought into the Western 
Hemisphere soon after the discovery of America and killed 
thousands of the Indians. It also affected the colonists. 
In 1721, Boston was ravaged for the sixth time by this 
disease. Out of the 10,567 inhabitants, 5989 had the 
disease and 894 died. 

In 1796, Jenner, an Englishman, demonstrated the fact 
that by inoculation of a person with cowpox, a disease 
peculiar to cows and in some way allied to smallpox, the 
patient would become immune to the dreaded disease. 
This was one of the greatest and most beneficial discoveries 
of medicine which has ever been made. 

As the result of vaccination and sanitation smallpox has 
become a rare disease in the civilized nations of the world, 
and is least prevalent where the vaccination laws are the 
most stringent. 

Vaccination for smallpox consists in the inoculation of 
the human patient with vaccine, a substance secured from 
a cow suffering from cowpox. This usually causes a slight 
illness, but during the illness the patient acquires a power 
which enables him to resist the germs of smallpox. This 
acquired power of resistance is called immunity. Im¬ 
munity secured through vaccination or through having a 
disease, such as whooping cough for example, is described 
as acquired immunity to distinguish it from that form of im¬ 
munity to all diseases or to certain diseases which many 
people possess. This latter is natural immunity. Those in 
the class who have not had measles may be said to have a 
natural immunity against measles. Those in the class who 
have had measles once have an acquired immunity against 
measles. 

Many people do not understand the theory of vaccina¬ 
tion and its advantages, and have opposed its use through 


ANTITOXIN 


511 


fear of acquiring lockjaw from the vaccine. It has been 
established that proper vaccine matter never contains the 
germs of lockjaw, and if this disease then occurs, it is due 
to failure in keeping the arm clean during the period when 
the vaccination scar is forming. 

Immunity to disease is now being produced through 
inoculation. The patient is inoculated, that is, there is 
introduced into his circulatory system a virus, or serum. 
Each disease has its own virus, as the vaccine in smallpox, 
and this virus produces a mild form of the disease. This 
causes the cells to become resistant to the germs or microbes 
of the specific disease. Inoculation is being widely used for 
the prevention of typhoid fever. All soldiers are required 
to take this treatment. It would be desirable for all people 
to become immunized against this disease, but those who 
travel extensively and thus have to drink all kinds of water 
and milk should certainly undergo this treatment. 

Vaccination and immunization reduce the liability of 
death in case the disease is acquired, but they do not abso¬ 
lutely prevent the disease. If a vaccinated or immunized 
person gets an overwhelming number of germs, he may have 
an infection of a slight kind. But the liability of contagion 
is reduced to a minimum. 

391. Antitoxin. — We cannot say definitely why vaccina¬ 
tion and immunization act as they do. It is known that 
if a poison (toxin) produced during a case of diphtheria 
is gradually introduced into the blood of a horse, a sub¬ 
stance is produced which destroys the injurious effects of 
the diphtheria poison. The serum from the blood of the 
horse is called antitoxin, and may be preserved for use at 
any time to destroy the influence of the diphtheria poison. 
A given amount of this antitoxin is introduced into the 
blood of the patient suffering from diphtheria, and usually 
counteracts the poison of the disease. This treatment has 
saved countless lives. It is estimated that in the ten years 


512 


PREVENTION OF DISEASE 


following the discovery of the diphtheria antitoxin the lives 
of a million children were saved in France alone. State 
boards of health usually furnish antitoxin for diphtheria and 
lockjaw. 

LABORATORY STUDY 

It takes five pounds of sulphur to disinfect a room which contains 
1000 cubic feet of air. Three ounces of forty per cent formalin, to 
which is added two and one tenth ounces of potassium permanganate, 
will also disinfect the same sized room. Compare the cost and ease 
with which each is used. 

392. Disinfection and Disinfectants. — The time when 
disinfectants shall be used and the manner of disinfection 
have been considered important factors in preventing the 
spread of communicable diseases. The purpose of disin¬ 
fection is to destroy the germs lodging on clothes, floors, 
carpets, and curtains. People who care for the sick should 
know where the germs are likely to be and how to disinfect 
places where they have found lodgment. The term disin¬ 
fectant is sometimes incorrectly applied to deodorizers, sub¬ 
stances which are used to destroy odors, but the word should 
be applied only to substances which destroy germs or bac¬ 
teria. 

Disinfectants are not expensive, and few of the patented 
preparations are as satisfactory as the common ones used 
by boards of health. Weak solutions of carbolic acid and 
bichloride of mercury are chiefly used for killing the germs 
on the hands and clothing, or for cleaning the woodwork in 
the sick room. Chloride of lime is used to kill the germs 
in the discharges of the body, and sulphur dioxide and 
formaldehyde gas for the final killing of the germs in the 
room or the whole house before it is occupied again. 

Never use any methods of disinfection unless they have 
been personally recommended to you by a physician or an 
expert in the details of room disinfection. Do not rely 


SAVE TEE CHILDREN 


513 


upon patented solutions and methods. The latter are ex¬ 
pensive and often practically worthless. 1 

393. Save the Children. — The care which animals take in 
the protection of their young is one of the most fundamental 
instincts of their nature. But in civilized man his instinct 
is broadened and controlled by the power of reason and a 
knowledge of the laws of hygiene. Until man came to 
understand these laws, many of his efforts to protect his 
young were of no more avail than the brave fluttering and 
plaintive cries of a bird when a red squirrel is robbing her 
nest. 

During the last decade there has been an attempt to re¬ 
duce deaths among children. It is lower in America than 
in most countries of the world, in which fact we take 
pride. The state of New York has the lowest death rate 
among children of any state in the world of which we have 
accurate knowledge. Yet there are communities in this 
state where the waste of infant life is a disgrace to civiliza¬ 
tion. The centers where this high death rate exists are largely 
populated by foreigners whom we permit to live in unhygienic 
conditions. 

In a study of 9912 deaths among infants in New York 
State for the year 1916, over 55 per cent of these died from 
measles, whooping cough, bronchitis, pneumonia, broncho¬ 
pneumonia, and infantile diarrhea. All of these are due in 
large part to parental ignorance concerning the elementary 
facts of sanitation and the proper care and feeding of infants. 
The infantile mortality among the foreign-born mothers is 
much greater than in the native white mothers. Particularly 
high death rates prevail among the Polish, German, and 
Austrian mothers. 

It is difficult properly to measure the value of health to 
the community. When the wage earner is sick and is placed 

1 When practicable, it is well to have the local health officer discuss such 
subjects as disinfection and quarantine. 



514 


PREVENTION OF DISEASE 


in quarantine, the loss of money is the amount he might 
have earned. In the case of a typhoid fever epidemic the 
total loss is many thousands of dollars. Further, there is 
no adequate measure of the sufferings of those who die and 
the heartaches of those who survive. But both the suffering 
and the financial loss can be greatly lessened by improving 
our sanitary laws and aiming at a better state of health for 
all the people. An increase in taxes to provide cleaner 
streets, public playgrounds, proper sewage disposal, and 
adequate inspection of milk, meat, and water, is really an 
economy. For although such improvements cost money, 
they are not so expensive as epidemics of disease and the 
maintenance of hospitals and of orphan asylums. 

394. Epidemics after Wars. — The return of two million 
men from Europe after living there for several months, to 
scatter throughout the United States, raised public health 
questions of great interest. After the Crimean War (1854- 
1856), cholera was epidemic in France and England; after the 
Franco-Prussian War (1870-1871), smallpox was epidemic in 
England, Germany, and Austria; after the American Civil 
War (1860-1864), typhoid fever spread to many of the 
northern cities ; and after the Spanish-American War (1902), 
typhoid and smallpox were very common. These historical 
facts show that there has been great danger in the past from 
returning troops. 

The officials in the army and navy thoroughly under¬ 
stood the dangers and tried to take proper precautions 
against the spread of disease ; but the task was very great. 
Some of the epidemic diseases in Europe were of the types 
which, once well started, might produce great havoc. They 
included trench fever, typhus, relapsing fever, cholera, and 
plague. Most of these are transmitted by vermin, most 
commonly the louse. In general the conditions are not favor¬ 
able in the United States for the transmission of disease by 
lice, although in certain congested quarters they are common. 


PREVENTION OF EPIDEMICS 


515 


The term epidemic as used in this paragraph refers to the 
widespread occurrence of a disease in which a large number 
of people in a community are affected at the same time. 
This is the usual sense in which it is used by physicians. 

All American troops were detained in Europe at foreign 
ports for two weeks, during which time they were deloused. 
After the troops had embarked, they were inspected a second 
time for lice. On landing in the United States, all the troops 
were sent to debarkation 
camps, where universal 
delousing was practiced. 

Many people think 
that Americans take so 
many precautions and are 
so well trained in ordi¬ 
nary questions of per¬ 
sonal and civil hygiene 
that epidemics are im¬ 
possible. While many are 
familiar with the ordinary 
rules which science has 
devised for their protection, it requires that all observe them. 
Those of us who understand the real meaning of communi¬ 
cable disease must take upon ourselves the responsibility of 
helping to explain the cause of all such disease to those who 
have not been so fortunate as to have had a course in biology. 

395. Prevention of Epidemics. — The first measure to be 
adopted, and the one of greatest importance, is educational. 
Under this heading is included the knowledge: (1) that all 
germ diseases are due to a specific germ, plant or animal, 
living in an intimate relation on or in the human body; 
(2) that all germ diseases are preventable; (3) that keeping 
our bodies clean, eating clean food, well cooked, and taking 
plenty of exercise will do more to prevent germ diseases 
than anything else. 



Figure 431. — Male and Female Cooties. 


These vermin greatly annoyed the 
soldiers in the trenches and are carriers 
of disease. (Much larger than in life.) 




516 


PREVENTION OF DISEASE 


The second important measure to be adopted to prevent 
an epidemic after the communicable disease has appeared is 
the prompt quarantine of the first cases and immediately 
putting into operation the regulations of the Board of Health 
for communicable diseases. 

398. Heredity of Disease. — The term heredity of disease 
is one which has been misunderstood by many people. By 
the term heredity we mean that which is handed on from 
parents to their offspring. In the case of biological diseases 
which are caused by some definite plant or animal, it is 
evident that they cannot be inherited. But when the 
parents are afflicted with a biological disease, their bodies 
become weakened 'and their offspring may have a poor 
constitution so that they are more easily affected by disease. 

397. Immunity. — Immunity is a technical term which 
means that the body resists or is not susceptible to the 
germs of biological diseases. Many persons do not become 
sick when there is an epidemic of typhoid fever, measles, 
malaria, or the like. Such persons are said to possess a high 
degree of natural immunity to disease germs. People 
usually well frequently take germ diseases when the body 
happens to be exhausted by care or work. In such cases 
the immunity of the body has been weakened. Many of 
the germ diseases confer immunity against a second attack 
of the same disease, but this does not hold true for all per¬ 
sons or for all germ diseases. Vaccination against smallpox, 
in the case of most persons, confers immunity for about seven 
years. Inoculation with the typhoid serum confers im¬ 
munity for from two to three years. Immunity, then, is a 
relative term, and depends in a large measure on the state 
of health of the individual and on his power of resisting the 
poisonous effects of disease germs. 

Some idea of loss of immunity is gained from a study of 
the increase in tuberculosis by Homer Folks, War, Best 
Friend of Disease, in Harper’s, March, 1920. 


PREVENTIVE MEASURES AGAINST SICKNESS 517 


Student Report 


Due to Some Plant or Animal 

Treatment by 


Prevented by 



In the water 

From contact 

Nature 

Medicine 

Antitoxin 

Personal care 

Quarantine 

Boiling the water 

Fumigation 

Killing flies 

Cold .... 
Measles . . . 

Whooping cough 



X 

X 



X 

X 

X 


Typhoid fever . 
Tuberculosis. . 

Add others . . 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 


398. Public Parks and Baths. — With the rapid growth in 
population of cities, more and more people are concentrated 
in limited areas. The trees are removed from the streets 
and the buildings crowd close to the sidewalk, preventing 
the growth of even small plots of grass. To offset this great 
disadvantage, cities have set apart parks, where trees and 
grass can grow and where those who cannot get to the coun¬ 
try may have contact with nature. 

Closely associated with the parks is the public bath, which 
is a large “ swimming pool ” where all may have a chance 
for refreshment and play. A certain amount of play is not 
only desirable, but necessary, if one is to maintain the vigor 
of health. These two features in the life of our cities are 
very useful in helping to keep people well. There are a 
number of other reasons why public parks and baths are 
desirable. What are they? 

399. Preventive Measures against Sickness. — Now that 
people have come to understand some of the real causes of 
disease, they feel that they should do everything possible 























518 


PREVENTION OF DISEASE 


to prevent it. A great deal of progress has been made and 
some states are far in advance of others in prevention of 
disease. We have really made only a beginning in this 
direction and by the time that you have become men and 
women many additional measures will be in operation to 
assist you and your children in keeping well. Reference 
has already been made on page 513 to some of the efforts 
that are being made in New York State to save infants 
from dying of preventable diseases. This is known as the 
Child Welfare Movement. What can you find out about 
this movement in your community? In this connection 
you should know about the work of the city or county 
bacteriologist and the health officer. 

The following notes were taken from the annual report 
of one of our New; York State cities: In the bacteriological 
office 10,872 diphtheria cultures were made; 399 examina¬ 
tions of blood, and 1293 cultures of the sputum of patients 
with suspected tuberculosis; 3073 chemical and bacterio¬ 
logical analyses were made of milk and 215 of cream. The 
drinking water of this city received repeated study, as the 
630 tests for bacilli coli indicates. There were 176 inocula¬ 
tions for typhoid and 973 miscellaneous studies. This does 
not include the work done by the division which has charge 
of vaccination against smallpox. Not only were the dairies 
near the city inspected but the more distant dairies were 
regularly examined. 

Closely associated with this technical work in the bac¬ 
teriology office was the work of the visiting nurse and 
the school doctor. In this same city nurses visited 3299 
homes during the year, and one school doctor made 2477 
physical examinations. He found 1845 cases of decayed 
teeth, 25 cases of poor eyes, and 36 cases of bad tonsils 
and adenoids. 

But the health of the city is cared for not only by looking' 
after the school children but also by inspecting food, and 


POWER OF HEALTH OFFICERS 


519 


we find that 31,897 carcasses of meat were passed on during 
this same year; while sanitary officers inspected yards, 
barns, cesspools, garbage, stagnant water, and other possible 
sanitary nuisances to the number of 9308. Learn all that 
you can about the extent and work of your health de¬ 
partment. 

Power of Health Officers .—To control communicable dis¬ 
eases is one of the most important duties of a health officer. 
Says Mr. Joseph A. Warren, of the New York State Depart¬ 
ment of Health: “ When the presence of a communicable 
disease has reached the proportions of an epidemic, the 
importance of this duty becomes intensive. From a legal 
viewpoint the question of the duty of the health officer in 
such circumstances resolves itself into one of power. A 
physician may ask: What should a health officer do ? A 
lawyer must ask: What can a health officer do ? The 
latest decision of the Court of Appeals (New York) holds 
that where a local ordinance provides for isolation or 
quarantine in any case deemed necessary by the health 
officer, then so long as the health officer acts in good faith 
and has reasonable grounds for his action, his action will 
be sustained. This situation emphasizes the importance of 
having proper local ordinances giving the health officer suffi¬ 
cient power.’ ’ 


SUMMARY 

As a physician knows the nature of a disease and its effect 
upon the body, he can aid materially in overcoming the ill¬ 
ness. Each biological disease is distinct and must have 
special treatment. Many of these diseases are taken from 
some one who has the disease. Vaccination, quarantine, 
and disinfection are measures which help to prevent the 
spread of germ diseases. It is our duty to keep well, and 
we can do much toward this by understanding how to avoid 
the biological diseases. 


520 


PREVENTION OF DISEASE 


QUESTIONS 

What is vaccination ? What is quarantine ? For what diseases are 
people quarantined? What is the work of the Board of Health? 
What is the purpose of disinfection? What are the chief disinfectants? 
What is the danger from epidemics? Name some epidemics. How 
can they be prevented? What are some of the values of public parks 
and public baths? What are the powers of health officers? What is 
your state doing to prevent disease? 

REFERENCES 

Chapin, Sources and Modes of Infection. 

Conn, Bacteria in Milk. 

Cornell, Health and Medical Inspection of School Children. 
Edelman, Mehler and Eichorn, Meat Inspection. 

Rosenau, Disinfection and Disinfectants. 


CHAPTER XXXVII 


BIOLOGY AND HUMAN PROGRESS 

Human progress may be defined briefly as the extent to 
which man has gained control of his environment and the 
use which he has made of this control. In a general way our 
environment has not undergone much change in the last 
thousand years and yet our control over it has undergone 
more change during the past hundred years than in any pre¬ 
vious thousand years. 

This great change is due largely to two factors: (1) scien¬ 
tific discoveries; (2) the intelligent application of these 

discoveries to the life of all the people. 

400. New Discoveries. — Keeping in mind the important 
fact that our universe has remained about the same during 
the past thousand years, the natural inquiry is : How can there 
have been so many new discoveries in recent years? This 
question can be easily answered. When some one finds 
a new animal or plant and announces that he has discovered 
this animal or plant, it simply means that man has seen 
and described it for the first time. This kind of animal 
or plant may have been living in this same region for 
hundreds of years. It is the same when some one makes 
a new discovery in physics or chemistry. He recognizes 
relationships that no one else has ever noticed. All new 
discoveries have been made by men and women who were 
just boys and girls as you are, with possibly no notion of the 
way that they were to help to make this world a better place 
to live in. There is still much to be learned about the 
relation of plants and animals to human progress and some of 

521 


522 


BIOLOGY AND HUMAN PROGRESS 


you should prepare yourselves by thorough study to have a 
part in this great work. 

In this chapter a brief account of the value and character 
of new discoveries in biology will be given. The examples 
selected, however, serve to show only a small aspect of the 
whole problem. But they illustrate that human progress, 
with respect to biology, is dependent upon our knowledge of 
the intimate life of animals and plants and the general laws 
governing their activities. These have been outlined in the 
previous pages of this book. Let us now select a few concrete 
examples and consider their relation to human progress. 

401. Insect Pests. — Most of us never realized how many 
different kinds of insects there were that feed upon even 
garden vegetables until we tried to do our part by caring for a 
war garden. Nearly all the thousands of plant diseases and 
pests that go to make the life of the farmer, gardener, or 
orchardist unhappy, and greatly to reduce the size or entirely 
destroy his whole crop, a few years ago occupied but small 
territories. So far as our information goes more than one 
half of the insects that cause incalculable losses in our fruits 
and vegetables came from foreign countries. They may 
be said to have migrated to the land of plenty, for in their 
native homes either the amount of food was limited by the 
growing of small crops or their natural enemies were so 
numerous that they were themselves destroyed before they 
could do any marked damage. 

At first thought it seems strange that the government of 
the United States should have a quarantine against insects 
landing at our sea ports, but that is just what the Federal 
Plant Quarantine Act of 1912 means. One department 
of our government is turning its attention to little insects in 
order to save American agriculture by preventing any more 
kinds of insects from, entering the United States. 

402. Fruit-flies.— Some of these insects of other lands that 
are serious pests are popularly known as fruit-flies. They 


FRUIT-FLIES 


523 



resemble house-flies, but are of more attractive appearance, 
inasmuch as their wings are prettily spotted and banded 
and their bodies are usually more brightly colored. They 
are like house-flies also in that they lay small eggs that hatch 
into whitish maggots. These maggots feed upon the living 
tissues of fruits, nuts, and vegetables. Eggs are laid just 
under the skin of the fruit and these eggs hatch into maggots 
that burrow in all direc¬ 
tions. As the maggots 
tunnel about they cause 
decay to develop and 
these decaying areas pro¬ 
duce greater injury than 
the maggots themselves. 

Increasing imports 
from the countries where 
fruit-flies now abound, 
the extension of trade 
to remote corners of the 
earth, and the growing 
density of population in 
the warmer parts of our 
country, are each year 
increasing the danger 
that fruit-flies may be¬ 
come firmly established 
in this country. In order 


Figure 432.—Adult Male Mediterra¬ 
nean Fruit-fly (greatly enlarged). 

This fly is a cosmopolitan pest. It has 
been known for one hundred years and 
during this time has spread throughout 
the world, North America being the only 
continent on which it has not become 
established. This fly does not harm man 
personally but is one of the most destruc¬ 
tive of the fruit-flies. 


to destroy fruit-flies, the 
Plant Quarantine Act prohibits the entry of all horticultural 
products likely to carry insect pests unless they have been 
rendered free from danger as pest carriers. 

The United States Department of Agriculture has issued 
the following explanation and regulations in connection with 
fruit-flies: The Bermudas probably would not now be in¬ 
fested by the Mediterranean fruit-fly had not a sailing vessel, 



524 


BIOLOGY AND HUMAN PROGRESS 


bound for New York from the Mediterranean region during 
Civil War times, been blown from her course and forced 



to unload her cargo containing infested fruits at St. George. 

The Mediterranean fruit-fly 
did not become established 
in Australia until steam¬ 
ships and cold storage made 
it possible for the infested 
Mediterranean countries to 
ship oranges to Perth and 
Sydney. With the pest 
established in eastern Aus¬ 
tralia the ships plying be¬ 
tween Australia and Hawaii 
carried the maggots to 
Honolulu, and to-day the 
inspectors of the state of 
California and of the United 
States are intercepting in¬ 
fested fruits on ships arriv¬ 
ing at San Francisco and 
San Pedro from Honolulu 
and Hilo. 

Some conception of the 
extent to which restrictions 
are placed is gained from 
the following list: Importa¬ 
tions of certain fruits from 
Mexico are prohibited ; also 
all pines from Europe, and 
five-leafed pines from Asia, 
Canada, and Newfoundland ; alligator pear seeds from Mexico 
and Central America; all citrus fruit stock from all foreign 
countries; Indian corn or maize and closely related plants 
from India, Siam, China, Malayan Archipelago, Australia, 


Figure 433. — Small Mango Fruit Cut 
to Show the White Larvae or Mag¬ 
gots Which Have Hatched from 
the Eggs of the Mediterranean 
Fruit-fly. 

These maggots burrow in all direc¬ 
tions through the pulp of the fruit, thus 
rendering it unfit for food. A single 
fly may lay as many as eight hundred 
eggs, depositing from six to ten eggs in 
each fruit. This fly is known to deposit 
her eggs in seventy-two different kinds 
of fruits. 





Dr. L. 0. Howard was born at Rockford, Illinois, 1857, and is 
still living. The year following his graduation from college, he 
became assistant entomologist in the Department of Agriculture 
at Washington. He remained in this official position until 1894, 
at which time he was made chief of the Bureau of Entomology. 
This position he still holds. He prepared definitions in entomology 
for the Century and Standard dictionaries. He is the author of 
Mosquitoes — How they Live; The Insect Book; The House-Fly; 
and many government publications. For many years he has acted 
as the permanent secretary for the American Association for the 
Advancement of Science, the largest body of scientific workers 
in America. 

Dr. Howard has devoted his main energies for the past forty 
years to applying the technical discoveries in entomology to 
human welfare. 




U. S. DEPARTMENT OF AGRICULTURE 525 


New Zealand, South Sea Isles, Philippines, Formosa, and 
Japan; sweet potatoes and yams from all foreign countries ; 
banana plants from all foreign countries including Hawaii 
and Porto Rico. 

403. United States Department of Agriculture. — The 

fruit-fly illustration introduces us to the larger study of the 
work of the Department of Agriculture and we may begin 
with one of its subdivisions, the Bureau of Entomology. 

During the past forty years Dr. L. 0. Howard has been 
either assistant director or director of this bureau. He and 
his numerous associates have been making discoveries about 
insects and applying to human welfare not only the new 
things that they have been learning about insects but the 
new discoveries made all over the world. 

We may gain some idea of the amount and kind of work 
done in this Bureau by simply reading over the following 
subjects, each of which received special study in this Bureau 
during the year ending August 1, 1917: Work on the gypsy 
moth and brown-tail moth; deciduous-fruit insect investi¬ 
gations ; southern field crop insect investigations; investiga¬ 
tions of the insects affecting the health of man ; insects affect¬ 
ing the health of domestic animals; cereal and forage insect 
investigations ; investigations of insects affecting forest and 
shade trees, forest products, and hardy shrubs; investiga¬ 
tions of insects injurious to vegetables and truck crops; 
stored-product investigations; insects affecting tropical and 
subtropical fruits ; bee-culture investigations. 

The extent to which man can control the multitude of 
insect pests and utilize the beneficial insects furnishes a good 
measure of human progress in this realm of biology. 

This outline of the work in the Bureau of Entomology 
reveals but one of several related fields of activity in which 
the United States Government is trying to help us gain 
control of our environment. You should become equally 
familiar with the other divisions of this work. This your 


526 


BIOLOGY AND HUMAN PROGRESS 


teacher will show you how to do. Here are the names of 
these bureaus : The Biological Survey, where they have been 
giving special attention to seals, reindeer, and ground 
squirrels; Bureau of Fisheries, which includes not only fish 
but also clams and oysters as well as lobsters, shrimps, and 
crabs; Bureau of Plant Industry, dealing with a wide range of 
problems connected with fruits, vegetables, cereals, and 
general farm crops; and the Bureau of Chemistry, which 
takes up such questions as sugar manufacture, various sirups, 
and adulterations. 

Many of the results of the discoveries of the experts 
working in the United States Department of Agriculture 
are published as Farmers’ Bulletins and can be secured by 
any one. Write to Division of Publications, Washington, 
D. C., for the list of available bulletins, which will be sent 
free so long as the supply lasts. 

404. New Ideas. — New ideas keep one informed about the 
way other people do and make one broadminded and pro¬ 
gressive. A different way of weaving cloth, a new process 
in the utilization of the stored energy in coal, or a better 
recipe for making bread indicate how a variety of ideas may 
help man to control his environment. Among the most 
fruitful sources of new ideas are the numerous scientific dis¬ 
coveries that are constantly being made. Such discoveries 
are of no value to the masses of the people unless they are 
turned to practical use. 

New ideas are rejected by many people because they do 
not understand the facts that have been discovered. In 
order that we may better understand this important phase 
of biology, we will now examine two interesting subjects, 
variation and heredity, and point out their relation to human 
progress. 

405. Variation. — One of the surest ways to understand 
the scientific meaning of the term variation is to collect 
leaves from any tree. Maple or oak leaves are especially 


VARIATION 


527 



satisfactory because of their irregular margins. When such a 
collection of oak leaves is available, try to find two that are 
identical in every detail. It will take but a few minutes to 
convince any one that the task is impossible. These dif¬ 
ferences which you have noted are known as variation. It 
is not correct to use this term variation to describe the dif¬ 
ferences that exist between maple and oak leaves, for example, 


Figure 434 . — Variation in the Size and Shape of Timothy Heads in 
the Same Kind of Timothy. 

(Photograph furnished by Cornell University.) 

or the differences that exist between a cat and a dog. In the 
study of variation, we can only contrast differences in the 
same kind of animals or plants. 

In Figure 434 is shown a photograph of the different sizes in 
the heads of timothy hay. The variations have to do with 
the length, thickness, and form of the head. In these heads 
are grown the seeds which are valuable as food to animals 
and they are used as seed when the farmer wishes to raise 








528 


BIOLOGY AND HUMAN PROGRESS 


a crop of hay. Figure 435 shows the practical value of planting 
seed that yields a large crop instead of a small one. In each 
of the five bundles in this figure, the same amount of seed 
was planted in the same kind of soil. Here we have a 
variation in the quantity of hay. 

The amount of variation in living things is only partly 
appreciated, as complete studies have not been made. In a 
recent study of wheat a great deal of variation was noted, 
as is illustrated by Figure 436. Wheat is raised for the purpose 
of obtaining as large a yield as possible of wheat kernels. 



Figure 435 . — Bundles of Timothy Raised under Identical Conditions 
from the Same Amount of Seed. 

It pays to plant good seed. (Photograph furnished by Cornell University.) 


A farmer who planted seed that produced plants with short 
and thin heads would harvest from ten to fifteen bushels 
per acre; while the one that planted seed that grew plants 
from which twenty-five to thirty-five bushels per acre could 
be had would be more successful. 

In order to furnish the farmer with the necessary informa¬ 
tion upon all such subjects, scientific experts have been and 
are now devoting a great deal of time to experimentation. 
The following examples are given to show the importance 
of such studies in helping man to make plants grow as he 
wishes them to grow and thus control his environment. 




VARIATION 


529 


The first example is a study of wheat. Figure 437 consists 
of bearded wheat, the pollen of which was placed on the 
stigma of the wheat flowers that formed on the non-bearded 
wheat shown at the right in figure. When the kernels of 
wheat in this head ripened, they were sown and a plant 



Figure 436 . — Variation of the Size and Shape of Heads of Wheat. 

All grown from the same kind of wheat. (Photograph furnished by 
Cornell University.) 







530 


BIOLOGY AND HUMAN PROGRESS 


produced which grew a longer head with practically no beards 
(the middle head in Figure 437). Such a head of wheat would 
yield more kernels of wheat than either of the parent heads. 

Now if the scientific ex- 



Figure 437 . — Heredity in Wheat. 


The head of wheat on the left of this 
figure has beards. The pollen from the 
wheat flowers of this head was placed on 
the stigma of the wheat flowers that grew 
in the head shown in the right wheat head 
of this figure. When these kernels of 
wheat ripened, they were sown and pro¬ 
duced a wheat plant that had more wheat 
kernels than either parent. This is the 
head shown in the middle. (Photograph 
furnished by Cornell University.) 


pert can make this new 
wheat plant permanent, 
that is, produce seed 
which will always grow 
large heads, he has fur¬ 
nished the farmer with a 
new kind of wheat and 
has made a new dis¬ 
covery. 

What does the scien¬ 
tific man do who makes 
such a new discovery? 
He starts out to tell just 
as many people as he can 
that he has made a new 
discovery and asks them 
if they do not wish to 
try it. In order that as 
many people as possible 
shall have an opportunity 
to know about his new 
discovery, he writes a de¬ 
scription of it and sends 
it to some scientific jour¬ 
nal. He does not get 
any pay for his scientific 


article as do writers of 
stories, nor does he have his article copyrighted, but he 
invites any one who wishes to use his facts. 

Another example has to do with variation in resistance to 
disease. The American grape is a North American plant 








VARIATION 


531 


including from fifteen to twenty-five different species, about 
one half of the total number known to man. These different 
kinds of grapes grow in varied areas and climates. Their 
original distribution over North America was due to animals, 
such as birds, and to river currents. 

The several varieties of American grapes are descendent 
from an original species which has become changed by 
environment until we find 
types of grapes as diverse 
as the regions in which 
they are found. 

Many of these varieties 
have been in existence 
since white men came 
to this country. During 
this time they have ac¬ 
quired a strong resistance 
to certain parasitic dis¬ 
eases which are very de¬ 
structive to the European 
grapes. Among them is 
one that is caused by a 
minute plant louse that 
lives either in the leaf, 
stem, or root. This in¬ 
sect is known as phyllox¬ 
era (fil-oks-e'ra) and is 
very destructive. In addition to this animal disease, there 
are three plant parasite diseases: black-rot, downy mildew, 
and powdery mildew. Each of these four diseases is able to 
kill grape plants and more than one may attack the same 
plant at the same time. 

A few years ago these diseases became widespread in 
Europe and threatened to destroy most of the European 
vineyards. Many experiments were undertaken to save 



Figure 438 . — Leaf Galls on Grape 
Caused by Grape Phylloxera. 


The roots are also injured by this dis¬ 
ease which threatened to destroy all of 
the European vineyards. 




532 


BIOLOGY AND HUMAN PROGRESS 


this valuable industry and it was discovered that the Euro¬ 
pean grapevine could be grafted on to the root of any one 
of several of the American grapes. When these vines were 
thus grafted, they were found to possess a resistance to these 
four diseases with the result that the vineyards of Europe 
were saved. 

This success was due to scientific study which discovered 
the difference between the European and American grapes 
in regard to their power to resist disease and the fact that the 
quality of the European grape would not be altered by grafting 
it on the roots of the American varieties. Here we have an 
illustration of variation that is not confined to the shape and 
size of the parts but to their resistance to disease. This may 
be described as an acquired immunity that is transmitted 
by heredity from one generation of grapes to another. The 
word immunity used in this last sentence was explained on 
page 516. If we explain the scientific meaning of heredity, 
this brilliant discovery in regard to grapes will mean more to 
you. 

406. Heredity. — An easy way to understand the technical 
meaning of this term which we use so frequently is to make 
a study of your hand. Normally we all have four fingers 
and one thumb but our hands are quite unlike. This is 
readily seen by comparing the three hands in Figure 439. The 
large one is the hand of father, the middle one of daughter, 
and the right one of mother. The first and the last fingers of 
the father’s hand are about the same length, while the little 
finger of the mother is much shorter than her first finger. 
This difference in the length of these two fingers is repeated 
in the hand of the daughter. We say that the daughter in¬ 
herited from her mother a short little finger and a long fore¬ 
finger. 

Now if we study the position of the thumb in its relation 
to the palm of the hand, it is seen that the distance between 
the thumb and the base of the forefinger is proportionately 


HEREDIT Y 


533 


greater in the hand of father than of mother. The same is 
true of the hand of daughter. When she grows to maturity, 
this distance will be much greater than it is in the hand of her 
mother. The daughter inherits this peculiarity in her hand 
from her father. 

Make a study of the several parts of your own hand and 
compare your hand with the hand of your mother and father. 



Figure 439 . — Heredity Shown by Comparison. 


Photograph of hand of father at the left, of mother on the right, and of 
daughter in the middle. Which parts of the daughter’s hand are like her 
mother’s ? Which like her father’s ? 

This study will show you what is meant by the term heredity 
as applied to your hand. 

In a similar manner you can compare the color of your 
eyes and hair; length of arm; shape of head; muscular vigor; 
size of body; intellectual traits, such as interest in language, 
history, science, or business; and temperament, which 
includes liveliness, deliberateness, excitability, quickness, or 
slowness. 




534 BIOLOGY AND HUMAN PROGRESS 

After you have made these comparisons, you realize that 
you are unlike both parents in that you have some features 
which are lacking in either your father or your mother. 
The total of the like parts and traits which are the same as 
in your father make up what you have inherited from your 
father; and the total of the parts and traits which are the 
same as those in your mother, make up what you have 
inherited from your mother. Thus we inherit from both 
parents. 

But there are usually found some structures and char¬ 
acteristics that do not represent anything found in either 
parent. If such are carefully analyzed, it is usually dis¬ 
covered that they exist in some of the grandparents. It is 
always interesting to try to locate their origin. 

This study of our hands and other parts of our body leads 
to an important general statement. All the parts of our body 
with their individual peculiarities have existed in other human 
beings and these persons were your immediate ancestors (parents, 
grandparents, great-grandparents, etc.). 

This explanation of heredity applies to all animals and 
plants, so that we can study heredity in our war gardens or 
with our pet animals. 

There is a limit to the differences that exist between child 
and parent, and these differences under normal conditions 
produce changes that would never make the structure a new 
one; for example, the finger is always a finger, and hair is 
always hair. Heredity is thus a descriptive, technical word 
used to explain the like parts between child and parent. 

During the past fifteen years, there has been a great deal 
of experimental work upon plants and animals in an attempt 
to explain just how an offspring inherits from its parents. 
It is impossible to record these experiments here because 
they would make a book several times as large as this one. 
It is too soon to be entirely certain just what these studies 
mean. When we do understand, then we can explain heredity. 


HEREDITY 


535 


Sufficient progress has been made in the explanation of 
heredity so that those who raise prize horses, cattle, sheep, 
apples, berries, wheat, and other products can be reasonably 
certain that their efforts will be successful. The average 
American cow gives 3100 pounds (a pound is about one 
pint) of milk a year; while one cow has a record of giving 
30,000 pounds in a single year. If the farmer can sell 
his milk for five cents a quart, the milk of the average cow 
would be worth $77.50 a year; while the prize cow would 
bring its owner $750. The variation in the amount of milk 
that a cow gives is an inherited character; so if the breeder 
selects animals that are big milkers, he can secure cows that 
will produce more milk than the breeder who does not make 
such a selection. 

In a similar manner all well-informed men who deal with 
animals and plants seek to secure certain results, but they can¬ 
not produce a new kind of animal or plant. They simply 
magnify some of the parts and reduce others by a detailed 
study of the way these parts are inherited. Sometimes they 
spend years and are not successful and often the desired 
result does not remain fixed or permanent but disappears 
in the next generation. This is a phase of biology that you 
should try to keep in touch with for both its interest and 
value. 

407. Relation of Variation and Heredity to Human Prog¬ 
ress. — In a general way this has already been indicated, 
especially where the practical value in raising larger crops of 
hay or wheat or in producing more milk was mentioned. But 
we are also interested to learn how variation and heredity 
apply to man. Your study of your hands and the other parts 
of your body demonstrated to you that you had inherited 
certain peculiarities from your parents. As you studied 
these similarities, you found that there were small differences 
or variations. This is well illustrated in the study that is 
being made of finger prints. Each one of us has these minute 


536 


BIOLOGY AND HUMAN PROGRESS 


lines following a general pattern with an infinite number of 
variations possible. It is these very small variations that 
each one has that enable the expert to identify two finger 
prints made by the same person. The United States Gov¬ 
ernment has selected finger prints as the surest way to identify 
its soldiers and many banks have long used the finger-print 
method of identification. 

Is it possible to predict what human beings will inherit 
from their parents? In a very general way we can answer 
this question in the affirmative. One of the most striking 
ways in which this is seen is in a study of the inheritance of 
certain defects, such as feeblemindedness. This is a disease, 
the cause or causes of which are not well understood, but we 
do know that such people are usually unable to earn a living 
and have to be supported by public taxation. A large pro¬ 
portion of their children inherit this same mental defect. 
The scientific study of heredity has proved that this is the 
case and always will be so. It remains for us to decide 
what is the best thing to do with such people. What is true 
of imbecility is not true of most other diseases. 

General ability and a tendency to industry and thrift are 
inherited by a large proportion of the children of the parents 
that possess these admirable traits. The men and women 
who possess such mental traits carry on the business of the 
country and pay taxes not only to support the government 
but also to care for the idle, the shiftless, and the criminal. 
If we have inherited these together with other valuable traits 
of character, we should take care that they are passed on to 
our children in order that the next generation shall possess 
enough men and women who will be able to advance human 
progress beyond our best efforts. 

408. Environment. — All through this book attention has 
been directed to the environment in which the animal or plant 
lived that was being studied. The same fact was empha¬ 
sized in the beginning of this section dealing with human 


ENVIRONMENT 


537 


biology. When the environment of man is critically studied, 
it is noted that it may have a large influence upon him. 
Even though he may have inherited a strong body and a 
tendency to thrift and industry, he may find himself in a 
social environment that is so strong that he has great diffi¬ 
culty in earning enough money to keep alive. When the 
full influence of environment was appreciated, men and 
women began to insist that better housing conditions and a 
certain amount of fresh air and light must be provided in 
order that those who lived in the tenements should find it 
easier to keep well and thus be able to work. Even though 
their environment be not of the best, it is possible for them 
to become superior to it. 

In the steady advance which human progress is making, 
the conditions under which men and women live and work 
are constantly growing better. As these conditions improve, 
there will naturally follow a larger opportunity for our in¬ 
heritance to have its full influence upon us. Two note¬ 
worthy movements are already having a marked influence 
in this direction; namely, the prevention of the spread of bio¬ 
logical diseases and the child welfare movement (see page 
513). As we gain a clearer conception of the importance 
to man of variation and heredity, other movements will be 
undertaken to place man in greater control of his environ¬ 
ment. 

The fact that biology stimulates us to think about all 
such problems is one of the main reasons for studying it. 
But with all this scientific information at our disposal, much 
remains for the individual to do. He must realize his 
obligations and opportunities in the age in which he lives. 
A mere passive existence has never accomplished anything 
worth while. The desire to serve our country and our fellow- 
man and a personal ambition must be added to our scientific 
information, if we would attain real success. 


PART TV 


GENERAL BIOLOGY-A REVIEW AND SUMMARY 

409. Living Things. — We are ready now to make some 
comprehensive statements -about animals and plants as we 
review the more important general facts. A few terms are 
employed to describe animals and plants, their structures 
and varied activities. Whenever you wish to make a gen¬ 
eral statement, such terms are indispensable. These terms 
are organism, organ, tissue, and cell. Associated with these 
four general terms is the word adaptation, which, like them, 
has a broad application. Explain why it is correct to apply the 
term organism to such different living things as the grass¬ 
hopper, horse, man, paramecium, corn plant, pine tree, and 
yeast plant. Write definitions of the remaining terms that 
will indicate their general application to all living things. 

Review the following : pages 1-4, 6-8; sections 30, 43, 89, 
90, 97, 98, 183, 197, 200, 252; and figures 1-5, 95, 98. 

410. Cellular Structure of Organisms. — We have seen 
that the root, stem, and leaf of the plant are made up of cells. 
Likewise the tissues found in animals are composed of cells. 
The human body with its organ systems, organs, and tissues 
is a grouping of cells. We find that all cells are much alike 
in structure and behavior, bringing these different and ap¬ 
parently unlike organisms still nearer together. 

Review the following : sections 8, 10, 109, 251; and figures 
4, 19, 47, 51, 65, 76, 197, 263. 

411. Protoplasm. — The active living part of all cells is 
the protoplasm. This is the part that grows, moves, and 
makes the organism live. In a green plant that looks fresh 

538 ' 


PRINCIPAL FUNCTIONS 


539 


and strong, it is the protoplasm that gives it that appear¬ 
ance. When a kitten runs and jumps, it is ‘the protoplasm 
of the cells that is active in reality. When a boy or girl 
skates or swims, we know that the good healthy protoplasm 
of the cells is at the bottom of such movements. So far as 
we can tell all protoplasm is much the same thing struc¬ 
turally and reacts in much the same way whether it is in the 
plant, kitten, or boy. 

When a plant grows, it is adding more cells; when the 
kitten grows, it is adding more cells; and the man is the boy 
with more cells added and more training and adaptation 
acquired. Nowhere in the animal or plant kingdom can we 
get away from the fact that the foundation of all organic 
structure is the cell. As each brick is a unit in a great 
building, so each cell is a unit in the huge tree by the road¬ 
side, the elephant in the zoo, or the great man leading his 
army. We are as old as our cells and the condition of the 
cells tells the story of health. Healthy cells make healthy 
bodies. 

Review the following : page 7; sections 6, 110; and figures 
4, 76, 195, 198. 

412. Principal Functions. — The principal functions of 
organisms are food-getting, digestion, assimilation, circula¬ 
tion, respiration, excretion, sensation, and reproduction. 
The food-getting methods of plants and animals vary widely. 
For the most part animals can move from a place of food 
shortage to another place where food is abundant. For the 
most part plants are anchored to a spot and must get their 
food there or starve. Animals take complex food sub¬ 
stances and break them down into simpler substances; 
while plants take simple substances and build them up into 
more complex substances. This is the great difference be¬ 
tween animals and plants as regards food-getting. 

The world is richer in food values because of the plants, 
whereas the animals tend to undo the work of plants. This 


540 GENERAL BIOLOGY — A REVIEW AND SUMMARY 


is the reason why plants have always preceded animals, as 
they have come to live first in one place, then another. For 
the same reason the quantity of food substances made by 
plants must always exceed the demand made upon them by 
animals, else the animals will starve. 

a. Food-getting in Plants. — Most plants get their food in 
the form of solutions through root-hairs and in the form of 
gases through the air. Root-hairs excrete substances that 
dissolve some otherwise insoluble materials and thus in¬ 
crease their food supply. Root-hairs are adapted to getting 
these solutions through their cell walls by osmosis. Leaves 
and young stems have stomata on their surfaces, which 
are openings that allow gases to pass through at certain 
times. 

Review the following: sections 241, 268, 273, 278; and 
page 306. 

b. Food-getting of Animals. — The simpler animals get 
their food in much the same way as root-hairs do, by simple 
osmosis. The higher animals have more elaborate structures 
for getting food. In the mammals, special organs, teeth, cut 
the food into smaller portions. It is then swallowed by 
muscles especially for that purpose and passed into the 
stomach. 

Review the following: sections 3, 5, 44, 58, 81, 99, 150, 
163, 174; and figures 3, 99, 106, 107. 

c. Digestion. — The food in the stomach of a mammal is 
acted upon by an enzyme secreted by the living cells lining 
the stomach cavity. Different enzymes grown in the living 
cells of the pancreas and stomach produce further changes in 
the food after it reaches the intestinal cavity. The action 
of these different enzymes is to reduce the foods to solution, 
which is digestion. The parts of the food that are thus 
digested are made soluble and pass by osmosis into the blood. 
Food in the food-vacuole of the paramecium is digested in a 
similar manner. The stored-up starch and protein in the 


PRINCIPAL FUNCTIONS 


541 


leaf or stem of a plant must also be digested before it can be 
absorbed. Enzymes play an important part in shortening 
the time that it takes to change foods into solutions. 

Review the following: pages 5, 13, 14,15; sections 114, 
120, 141, 206, 237, 246, 268, 326, 328; and figure 167. 

d. Assimilation. — After food has been digested, it is 
absorbed. In the paramecium or yeast cell, it is taken at 
once into the living protoplasm. There are no special 
structures such as are found in all complex organisms. The 
food is distributed throughout the cell. This simple condi¬ 
tion is not adequate when organisms are made up of thou¬ 
sands of cells and special methods of distributing the absorbed 
food are found. 

e. Circulation. — The organs of circulation in higher 
organisms may well be compared to our transportation 
systems, the railroads. Their chief function is to carry 
food, oxygen, and bodily wastes from one part of the body 
to another. In animals this system is known as the heart, 
arteries, capillaries, and veins; and in plants, as the fibro- 
vascular system of veins. 

Review the following: sections 48, 110, 114, 120, 141, 233, 
236, 237, 247, 248, 329, 357; and figures 64, 235, 256. 

/. Respiration. — Oxygen furnishes a necessary amount 
of energy to all organisms. Animals that live on land have 
special organs, the lungs, that are adapted to taking oxygen 
from the air; while aquatic animals, like fish and crayfish, 
have gills that are adapted to take oxygen from the water. 
Some animals, like the earthworm or hydra, have the cells 
covering the body adapted for this work. Plants have their 
leaves modifed by stomata, and through these oxygen passes 
into the plants. Under some conditions, the stem takes up 
oxygen. Aquatic plants, like algae, take up oxygen through 
the walls of the filament. 

Review the following: pages 5, 10, 15; sections 6, 46, 59, 
72, 115, 121, 142, 164, 175, 207, 237, 353; and figure 64. 


542 GENERAL BIOLOGY —A REVIEW AND SUMMARY 

g. Excretion. — The energy used by organisms in their 
several activities results in the formation of various wastes. 
These wastes are usually in the form of a gas, as carbon 
dioxide, given off in respiration by animals and plants, or as 
a liquid when discharged from the sweat glands and kidneys. 

Review the following : page 5; sections 8, 47, 61, 73, 116 ? 
122, 142, 165, 176, 237, 249, 358; and figure 73. 

h. Sensation. — We do not know whether we have more 
than five senses, but no matter how many there may be, all 
require that special cells respond quickly to various stimuli, 
such as light, heat, sound, etc. Such cells help man to 
understand his environment, and the more he trains his 
sense organs, the greater will be his capacity to enjoy nature. 
If our sense organ cells were not connected with the brain by 
nerves, they would be of but little use to us. Man has the 
most highly specialized brain of any animal. 

Most animals have sense organs and some form of a 
nervous system. The presence of such organs indicates a 
form of division of labor. But there are animals without 
sense organs or a definite nervous system. Such animals 
rely upon the general sensitiveness of the protoplasm to 
make them aware of changes in their environment. Plants 
do not have sense organs or a nervous system, yet they 
respond to light and dark, summer and winter. 

Review the following: page 6; sections 6, 49, 62, 74, 77, 
110, 123, 143, 177, 363; and figure 74. 

i. Reproduction. — The unicellular plants and animals 
reproduce in a very simple manner by fission. In multi¬ 
cellular organisms reproduction begins in a single cell, the 
germ cell. This germ cell has the power to carry on a pro¬ 
gram of development that varies but little for all eggs of one 
kind. The fish egg and the frog egg look much alike, but 
each follows its own individual order in development until 
the adult stage is reached. There is no mistake, and the 
development is never interrupted, and there can be no pause 


INTERDEPENDENCE OF ANIMALS AND PLANTS 543 


without disaster to the life of the forming organism. An 
egg may be kept before starting to hatch; but once started, 
it must continue. There is considerable variation in the 
exact manner in which the eggs of different animals develop. 
Some have a very large amount of food stored in the egg, as 
hens’ eggs, which influences the manner of embryonic growth. 

Review the following : page 6; sections 10, 50, 63, 67„ 75, 
84, 92, 117, 124, 134, 144, 145, 167, 178, 275, 281, 286; 
page 305; and figures 66-67, 75-80, 180, 191, 193. 

413. Interdependence of Animals and Plants. —As we 
have seen, plant life must precede animal life. Plants can 
take water, carbonic acid, and a few minerals, and make 
starch, sugar, proteid, etc. Before there were any animals 
on the earth, the plants were thriving and building foods. 
These foods with no animals to eat them decayed and made 
up rich soils for further plant growth. This continued till 
the animals appeared on the earth. 

These animals ate some of the foods that the plants made 
and in time died and their bodies together with the dead 
plants went back to the soil and made it still richer and able 
to produce better and more nourishing foods. This process 
has been going on for ages, and the plants have been furnish¬ 
ing the food for the animals’ bodies. At death the animal 
body goes back into the soil, making it richer in plant food 
and able to produce more plants and better food crops. 
Thus the plants are helped by the decaying animal bodies, 
and the animals themselves must have the plants for food 
during their life time. 

Of course, some animals eat flesh, but eventually in tracing 
back we come to the animal that feeds upon the plant food. 
The house cat, for example, eats mice, but the mice eat 
grains, and so we find the cat, a flesh-eating animal, depend¬ 
ent on animals that must have plant food. 

Review the following: sections 1, 15, 21, 28, 185, 245, 
311, 314. 


544 GENERAL BIOLOGY —A REVIEW AND SUMMARY 

414. Relation of Animals and Plants to Man. —No summary 
of a general course in biology would be complete that did 
not indicate some of the general relations of living organisms 
to man. They are our indispensable friends or unceasing 
enemies. The story of how man has come to control the 
multitudes of living things is as full of interest as it is im¬ 
portant to the continuance of a progressive civilization. 
There still remains much for man to discover, but we should 
be intelligent about what has already been accomplished. 

Man makes a greater use of the plant world than any 
other animal, and he uses the animal world for his benefit 
far more than any other animal. Because man is the highest 
type of animal he has gained mastery over plants and 
animals. Those nations that have found out the best ways 
to utilize the greatest number of plant and. animal products 
are the dominating powers of the world. Closely associated 
with man’s utilization of the organic world is his greatly 
improved use of natural forces and of the inorganic world. 

Review the following: sections 16, 66, 107, 136, 148, 158, 
160, 169, 182, 195, 208, 257, 263, 269, 270, 282, 289, 294, 
295, 296, 299, 300, 310, 315, 330, 333; page 296; chapters 
II, XXXV, XXXVI. 

415. Community Life. — It has often been said that man 
is a social animal. Man is not the only social animal. The 
communal life of the honey-bee, ants, and termites shows 
many wonderful examples of labor for the benefit of a whole 
colony. The honey-bee, when first out of the cocoon, as 
an adult is a nurse for the larvae, later a wax-maker for the 
colony, and later a field worker, a gatherer and maker of 
honey. Most of the work of the midsummer honey-bees is 
for others, since they die before winter begins. Conse¬ 
quently these bees are community builders in a real sense 
of the word. Ihose insects that have the greatest number 
of workers and the most extensive division of labor are the 
most successful in the struggle for existence. When we 


COMMUNITY LIFE 


545 


find the lower animals, especially insects, succeeding in their 
struggle for existence because of their community life, we 
do well to apply some of the lessons of the honey-bee to our 
life as members of a community. Honey-bees are instinc¬ 
tively sanitary. When an insect too large to move is killed 
in their hive, they embalm it. This tends to make the hive 
sanitary. Man in building sewage disposal plants and sewer 
systems is improving the health of the community. It is 
for the best interests of the majority that such care be taken 
with regard to public health. 

Honey-bees remove all waste pieces of rubbish, dirt, and 
loose pieces of every description from their hives. If a 
larva dies in the comb, the bees remove it and scrape and 
polish the wax directly. Honey-bees have epidemics such 
as “ foul brood.” The bees that clean their hives most and 
work the hardest to keep clean are quickest to recover. 

Human animals are subject to epidemics, and those that 
work the hardest to keep clean and use care recover most 
quickly. Man has learned that many diseases are conta¬ 
gious, and quarantines are maintained to prevent their 
spread. 

Bees never enter the hive of another colony unless to rob 
it of honey. But foul brood often kills or weakens an 
entire colony and the robber bees who enter and steal the 
honey carry home also the disease and thus it spreads. If 
the honey-bees maintained their usual habit of not going 
into other colonies, the disease would spread with difficulty. 

Bees act from instinct, and man is endowed with reason 
in addition to his instinct, and, naturally, we find man at his 
best carrying on a much broader line of community activi¬ 
ties ; for example, setting aside large tracts for public parks, 
in order that all people may go and enjoy the growing plants 
and see the animal life in its varying aspects. 

Man is improved mentally and spiritually by getting away 
from the daily routine of a business or professional life and 


546 GENERAL BIOLOGY — A REVIEW AND SUMMARY 


coming in contact with the great world of nature. So we 
find that as man is compelled to live in cities, where highly 
specialized conditions deprive him of the pleasures of the 
natural world, he is constantly adding to the parks and 
“ breathing places ” where he may go and “ commune ” 
with nature. 

Everywhere we see this tendency of man’s nature to get 
into contact with the real, natural world. House plants, 
birds in cages, bird-nesting boxes in the yard, trees by the 
roadside and flower gardens at the door — all these are re¬ 
sults of man’s efforts to commune with nature. 

Review the following : section 29; and figures 33, 37. 

416. Conservation. — As man has utilized some of the 
plants and animals for his advancement he has, in many 
cases, so wantonly handled them that there is danger of the 
supply being exhausted. In his haste for lumber to build 
houses and barns, he is selfishly cutting down trees in great 
quantity and leaving not sufficient to grow for the next 
generation. In his anxiety to get a big catch of fish, he has 
been catching so many as to leave none to lay the eggs for 
a new generation. Almost before we were aware of the dam¬ 
age that was being done, some animals and plants had been 
exterminated. 

Now we are looking ahead to see where the future lumber 
is going to grow; as a result we have forestry schools. Now 
we are thinking of the wild life that is growing less in num¬ 
bers and variety, and we are passing laws to protect it. Some 
one has said that we are merely guardians of the wild life, 
and that we must account for our stewardship to the gen¬ 
erations that come after. It would not do to pass on to 
future generations an earth depleted and robbed of wild 
life and made up of barren hills and rain-washed slopes. 

So we are interesting ourselves in this big question of con¬ 
servation, which is really acting as stewards of the earth 
for the benefit of the people who are to follow us. Every 


PUBLIC HEALTH 


547 


one can plant trees, make gardens, and protect and feed the 
birds ; and so every one may be a conservationist. 

Review the following: sections 66, 95, 96, 97, 100, 101, 
317, 318, 319, 322, 323. 

417. Public Health. — While we are conserving wild life 
and planning that the next generation may have a world 
rich in objects of natural beauty, there is danger that we may 
forget our own health. We owe it to the world to keep in 
good health. When we are ill we are not preparing for 
work, and we are not producing anything of value. We are 
taking the time of physicians, nurses, and friends, and pre¬ 
venting them from doing other work that would make the 
world a better place to live in. 

When we are ill it is generally because some one has been 
careless. It may not be our own carelessness, but gen¬ 
erally some one is at fault. For violating nature’s laws we 
generally pay the price — sometimes at once, sometimes 
later. It is our business to know these laws and then to 
obey them. We are coming to think of public health as 
something that may be bought. For example, water sup¬ 
plies may be protected and purified, if we install the proper 
equipment. This costs money, but pure water will make a 
community healthier, and it is worth money to a community 
to have all its people well, for they can work and add to the 
value of property. 

Certain diseases may be prevented if vaccines and anti¬ 
toxins are prepared and used at the proper time. The 
making of these vaccines costs money, but they may be 
purchased. So we are right when we say that public health 
is purchasable, provided we know what to purchase and 
how to use what we purchase intelligently. So we find 
various states with departments of health that are trying 
to improve the health of the people and lower the death rate. 
It really pays the state in money if it can lower the death 
rate. 


548 GENERAL BIOLOGY — A REVIEW AND SUMMARY 

The United States has its department of health that tries 
to prevent diseases from other countries from entering our 
land through ports and harbors. More and more the dis¬ 
coveries of medical men and biologists are making people 
healthier, and it is our duty to acquaint ourselves with the 
new discoveries bearing upon matters of health. 

Review the following: sections 29, 35, 160, 182; and 
figures 45-47. 

418. Departments of Agriculture and Forestry. — Aside 
from the health work of the states and the national govern¬ 
ment we find them active in many other fields. Among 
their other important functions is that which deals with 
crops and their enemies, new ways of treating the soil, con¬ 
trol of seed testing, analysis of various fertilizers, and many 
other kinds of work that have to do with farming and for¬ 
estry. 

There are so many other uses of forests than simply fur¬ 
nishing lumber that certain forests are not used for lumber 
at all. The regular flow of some rivers and spring streams is 
due to the permanence of the forests on their watershed. 
Take away the forests entirely and many springs would not 
furnish water in dry seasons, many streams would dry up, 
and fish would die. 

The forests are important directly and indirectly to many 
people. Recently the people of the State of New York 
voted to buy thousands of acres in the Adirondacks in order 
that all the people might have some of the benefits that 
come from forests. The reclaiming of arid lands and making 
them productive in the Western States is another govern¬ 
ment activity that has to do with agriculture and the in¬ 
creased production of food crops. 

Review the following: section 182; and chapters XXVII, 
XXIX. 

419. Plant and Animal Improvement. — We are accus¬ 
tomed now and then to hear discussions that give an idea 


NATURAL AND ARTIFICIAL SELECTION 549 


that the things of years ago were as good as those of our 
day, or better. Some say the apples of years ago were 
better or kept better or yielded better than the ones we raise 
to-day. As a matter of fact, apples, peaches, oranges, wheat, 
corn, and all the products of the soil to which man has given 
serious attention are bigger, better, and yield more than 
ever before. By careful selection of seed, larger yields of 
superior crops are easily attainable. The state and national 
governments maintain experimental stations where work of 
this nature is carried on. Much other valuable work in 
the way of insect control and soil study is done at these 
stations. 

420. Natural and Artificial Selection. — In nature there 
is a constant struggle among all living things for place, food, 
and opportunity. Whatever aids a plant to grow and shade 
another plant will give the winning plant an advantage. 
Whatever gives an animal protection from its enemies will 
enable that animal to survive. Some do not find protec¬ 
tion and thus perish. Nature selects those forms of life 
that are best fitted to meet all the natural requirements of 
the world where they live. 

Man steps in and selects animals for other reasons than 
those before mentioned. Man may want a fruit of a cer¬ 
tain flavor, or flowers of a certain color, or milk containing a 
certain amount of butter-fat, or corn with a certain number 
of rows of grain on a cob, and he selects the seed that will 
help him do this, or he selects the cows that will give milk 
rich in butter-fat, and eventually he may find what he 
wants. 

Whatever selection man may make is artificial selection, 
while the selection that is made in the world outside of man’s 
control is natural selection. It is natural selection that has 
done the most to make the great variety of plants and ani¬ 
mals in the world, and it is competition, with the elimination 
of the weak and unfit, that makes for the improvement of 


550 GENERAL BIOLOGY — A REVIEW AND SUMMARY 


the races of plants and animals. A world without competi¬ 
tion would degenerate and would be impossible in the con¬ 
dition that we know it. 

Review the following: sections 80, 103, 104, 105, 106, 208, 
320, 321; and page 270. 


INDEX 


References are to pages 


A 



Age of trees, how told 

266 




Agencies of seed distribution . 

241 

Abdomen, of crayfish . 


60 

Aggregate fruit. 


of grasshopper . . . 


23 

Agriculture, amount and kind 


Abnormal growth of tissue 


of cultivation in . 

231 

cause of disease 


487 

education for. 

245 

Absorbing pads of dodder 


253 

as an industry. 

245 

Absorption, of food, defined 

5, 

413 

influence of on civilization . 

296 

of food not nourishment . 


415 

Air, home of bacteria .... 

310 

Absorption in leaves 

of 


Air cells of lung. 

444 

Venus’s fly trap . 


367 

Air chamber of marchantia . 

331 

Accessory fruits . . . . 


237 

Akene . 

237 

Accessory parts of flower 


198 

Albumen, example of protein . 

416 

Acid medium in stomach 


411 

Alcohol, ambition destroyed by 

482 

Aconite, a poison . 


479 

a narcotic. 

479 

source of. 


297 

a poison. 

487 

Acquired immunity 


510 

and disease. 

506 

Action of voluntary muscle . 


438 

and patent medicines . ’ . . 

506 

Active bacteria reduced 

in 


cause of disease. 

487 

number by heating milk 


314 

chemical composition of . 

415 

Adam’s apple . 


445 

effect of, on circulation 

456 

Adaptation, discussed . . . 


1-4 

on digestion. 

430 

Adaptations, of honeybee 


49 

on nervous system . . . . 

480 

of fleshy fruits .... 


239 

formed by yeast plant . 

321 

of fruits for distribution 


in bread driven off by heat . 

427 

by animals. 


241 

not a food. 

416 

of fruits to distribution 

by 

/ 

Protozoa and. 

150 

water. 


241 

shortens life. 

478 

of a leaf . 


287 

use of in consumption . . . 

492 

of reptiles . . . . . 


104 

Alcoholism a disease .... 

482 

of the seed. 


219 

Ale, use of yeast in making . 

321 

of wood. 


263 

Alfalfa, member of pulse family 

299 

Adenoids . 


449 

root system of. 

252 

Adductor muscles of clam 


186 

Algae, class of Thallophytes . . 

9 

Adulteration, of cereals . . 


428 

lack of conducting system 


of foods. 


428 

in. 

370 

of milk. 


428 

Alimentary canal, of frog . . 

86 

Adventitious roots .... 


252 

of man. 

404 

experiments to show . . 


379 

Alkaline medium in mouth . . 

411 

Aerial roots . 

251, 

252 

Alligators, classified .... 

9 

Afferent fibers . 


470 

described. 

104 

Agar-agar, formula . . . 


312 

example of reptiles .... 

99 


1 

























2 


INDEX 


References are to pages 


Alternate leaves, of beech 


Anopheles, mosquito . 


55 

family. 

297 

cause of malaria . . . . 

55, 493 

of parsley family .... 

300 

Antennae of grasshopper . 


22 

of pulse family. 

299 

Anterior adductor muscle 

of 


of rose family. 

298 

clam. 


186 

of walnut family .... 

297 

Anther, described .... 


198 

Alternation of generations, 


Antheridia of fern .... 


336 

in coelenterates. 

166 

of moss. 


329 

in ferns. 

336 

of marchantia .... 


329 

in mosses. 

330 

Anti-pain medicines . . 


507 

Althaea, member of mallow 


Antitoxin, defined .... 


511 

family. 

299 

described. 


511 

Altricial birds, defined . . . 

113 

in preventing spread of dis- 


American elm, scientific name of 

10 

ease. 


507 

American grape, immunity of . 

530 

use in diphtheria.... 


507 

American Medical Association 


Ants, example of Hymenopte 

ra 

45 

503, 505 

social life of. 


53 

Ammonia in test for protein 

228 

Anus, in digestive system 

of 


Ammonium tartrate in Pasteur 


man. 


409 

solution. 

322 

Aorta, largest artery in man 


453 

Amoeba, classified. 

8 

Aortic arches of earthworm . 


182 

described. 

143 

Apetalous flowers .... 


202 

discussed. 

144 

Aphis, woolly. 


32 

respiration of. 

145 

Apiary, escape of bees from . 


45 

Amount of sleep required . . 

476 

Appendages of grasshoppers 


23 

Amphibians, described 

82 

of crayfish. 


60 

economic importance of . 

97 

Appendicitis. 

. 

408 

example of. 

9 

Appendix, vermiform . 


408 

laboratory study of. . . . 

82 

Apple wood, use of . 


352 

number of. 

9 

Apples, a form of fruit 


236 

summary of. 

98 

example of pome . . . 


237 

Amphioxus, notochord of . . 

69 

produced by rose family . 


298 

Amylops in a ferment.... 

412 

Aptera, order of insects . . 


29 

Anesthetic, defined .... 

479 

Aqueous humor. 


473 

dissolves lipoid. 

480 

Arachnids, list of ... . 


65 

Angiosperms, classes of f . . 

9 

Arbutus, destruction of . . 


395 

defined. 

9 

Arch, of foot. 


434 

Animal biology. 

17 

of hypocotyl of bean . . 


220 

Animal parasites, habits of 176, 

177, | 

Archegonia, of fern . . . 


336 

488, 494 

of moss. 


329 

Animal preserves, purpose of . 

395 

Arctic regions. 


371 

Animal starch, in liver . . . 

414 

plants of, modifications of 


371 

Animals, agents in distribution 


use of lichens in ... . 


326 

of seeds. 

241 

Area of forests. 


348 

decomposed by bacteria . . 

310 

Arms, example of organ . 


7 

without a backbone . . . 

8 

of starfish. 


169 

Annelida, a class of worms . 

175 

Army worm, harmful insect. 


41 

Annual rings, age of tree told by 

342 1 

Arsenic, a poison .... 


487 

in longitudinal sections of 


Arteries, function of . . . 


452 

trunks. 

291 

in circulation of clam . . 


187 

in stem of pine. 

342 | 

of crayfish. 

. 

64 













































INDEX 


3 


References 


Arteries — continued 

of fishes. 75 

of man.452 

Arthropods, classified .... 9 

example of. 9 

number of. 9 

word explained.60 

Arthropods, summary of . . . 67 

Articulation of bones .... 434 

Artificial respiration .... 448 

Asepalous flowers. 202 

Aseptic, defined. 313 

Asexual reproduction, of ccelen- 

terates.163 

Ash, result of chemical change . 10 

Ash tree.364 

Ash wood.352 

Asparagus, a leafless plant . . 290 

beetles. 34 

fern, specialized stem of . . 263 

Assimilation, defined .... 5 

in plants.282 

Aster, a common weed . . . 301 

Atmosphere, composition of 11 , 12 
Attitude of early settlers 

towards forests .... 348 

Auditory organ of grasshopper . 24 

Auricles of heart.452 

Aves, class of vertebrates . . 9 

B 

Bacilli coli, tests for . . . . 518 

Bacillus, a form of bacteria . . 309 

Bacillus tuberculosis, cause of 

consumption.489 

Bacteria, action on lava . . . 375 

carried by insects .... 29 

cause of sour bread .... 427 

cause of sour milk . . . . 314 

classified. 9 

conditions necessary for 

growth.310 

control of.313 

decomposition of materials 

by.310 

discussed.309 

distributed by flies .... 29 

effect of enzymes and . . . 311 

forms of.309 

harm to teeth from .... 407 


are to pages 


Bacteria — continued 

harmful. 314 

helpful. 309, 311 

important plants .... 309 

in formation of soil .... 375 

injury caused to plant by . 315 

inoculation of soil with . . 259 

in relation to milk . . . . 313 

in roots of leguminous plants 

256, 311 

in warm milk.316 

laboratory study of. . . . 312 

life processes of.310 

multiplication of .... 311 

presence, in polluted water . 462 

prevention of growth of . . 497 

proper conditions for growth 

of.310 

shape and size . . . 309, 310 

source of disease .... 489 

summary of.317 

unfavorable conditions with¬ 
stood by.311 

where found.309 

Bacterial poison, toxin . . . 311 

Bailer in gill chambers of cray¬ 
fish .63 

Balanced diet.418 

Balancing, use of fins for . . 73 

Balancing organ, ear a . . . 475 

Ball and socket joint .... 435 

Balsam, adventitious roots on . 254 

Balsams, conifers.345 

Balsa wood.356 

Bananas, value of as food . . 245 

Barberry, host of black stem 

rust.388 

Bark of hemlock.346 

Barley, a cereal.244 

a monocotyledon .... 227 

member of the grass family . 295 

Barnacles, economic importance 

of.65 

Bass, a bony fish.71 

example of fish. 9 

Basswood, characteristics of . 352 

Bast fibers.262 

Bat, enemy of mosquito ... 56 

Beaks of birds, variations in . 109 

Bean, an irregular flower . . 204 

embryo, growth of ... . 220 






























4 


INDEX 


References 


Bean — continued 
example of dicotyledons . . 9 

foodstuffs in.228 

fruit of.237 

germination of.220 

seed, laboratory study of . . 227 

seed, relation to flower . . 219 

seedling, parts of .... 220 

source of protein .... 228 

Bean (pulse) family, members 

of.299 

Bean weevil.34 

Beans as food.222 

Beaver.137 

Bee, culture investigations . . 525 

Bee farms, escape of bees 

from.48 

Bee fly, a beneficial insect . . 54 

Beech, value of.297 

Beech family, description of . 297 

Beech leaves.297 

Beef extract, in agar-agar . . 312 

Beer, use of yeast in making . 321 

Bees, classes of.46 

classified insects. 9 

complete metamorphosis of . 28 

drone.46 

gathering of nectar and pollen 

by.208 

honey, value of.49 

imperfect female (worker) . 46 

life history of. 46 

members of Hymenoptera . 29 

nurses.46 

perfect female (queen) . . 46 

swarming. 48 

wax, value of.49 

Beet, a dicotyledon .... 227 

biennial plant.252 

source of sugar.255 

storage of food in ... . 255 

Beetle, May, a harmful insect . 34 

potato, a harmful insect . . 35 

Beetles. 34 

bird enemies of.35 

example of complete meta¬ 
morphosis .28 

Belladonna, compared with 

stramonium.300 

source of.300 

Belly of muscle.438 


are to pages 


Berkshire pigs.133 

Berry, a form of fruit . . 233, 237 

collection of drupes.... 239 

defined.233 

Biceps muscle.438 

Bichloride of mercury, use of . 512 

Biennial roots.252 

Bilabiate flowers of mint . . 300 

Bile, a digestive juice .... 412 

Binding effect of roots . . . 256 

Biological diseases, kinds of . 488 

Biological problems involved in 

the production of food . . 420 

Biological survey.526 

Biological terms defined ... 1 

Biology and human progress 521 

Biology, defined. 6 

progress of.521 

Birds, characteristics of . . . 107 

classified. 9 

economic importance of . . 114 

number of. 9 

summary of.124 

Bird’s-eye maple.352 

Bird’s feet, different kinds of . 108 

Bitter, a fundamental taste . . 405 

Bittern, beak of.109 

Bivalves, reason for name . . 189 

Blackberry, in plant succession 375 
receptacle of fruit eaten . . 239 

Blackbirds, food of 35, 43, 115 

Black snake, a constrictor . . 102 

Black mustard.223 

Black raspberries.272 

Black rot. 531 

Black stem rust.... 380, 384 

Black walnut lumber .... 352 

Bladder in man.458 

Blade of leaf, food storage in . 276 

Blanching of celery .... 293 

Bleeding in plants.269 

Blood, corpuscles. 449 

of man. ’ . . . 449 

plasma. 449 

pressure in man. 454 

supply of muscle .... 438 

vessels, function of . .451 

Bluebird, a beneficial bird . . 114 

destroyed by hawks . . . 115 

destroyer of Lepidoptera . . 42 

food of. 144 



























INDEX 


5 


References 


Blue jay, feeds on larvae of 

Lepidoptera.42 

Blue racer, a constrictor . . 102 

Boa-constrictor. 102 

Boards of Health.507 

Bobolink, food of. 117 

migratory habits Qf . . 111,112 

nesting habits of . . . . 112 

Body, parts of in fish ... 71 

Body cavity of earthworm . . 180 

Body temperature of birds . . 110 

of mammals.125 

of man. 459 

Bone ache.492 

Bone, cells of. 433 

structure of.436 

Bones, broken. 435 

Boneset, medicinal plant . . 292 

Bony fishes, examples of. . 71 

Borax, a preservative . . . 314 

in cosmetics.504 

Borers, harmful beetles ... 34 

eaten by downy woodpecker 114 
Boric acid, a preservative . . 314 

Botfly, harmful insect.... 54 

Bottling, good and bad . . . 315 

Boxwood, use of.352 

Bracken fern. 333 

Bracket fungi, effect on trees . 324 

Brain, efficiency, discussion of . 476 

efficiency, conditions neces¬ 
sary for.476 

“ Brain ” of earthworm . . . 181 

Braincase of frog. 88 

Bran, used as an adulterant . 428 

Branch, example of organ . . 7 

of pine, position of ... . 342 

Brazil nut, a seed.245 

Bread, crumbs for feeding sta¬ 
tion .117 

making.426 

mold.323 

mold, laboratory study of . 325 

use of yeast in making . 426, 427 
Bread-making, scientific basis 

of.321 

temporary by-products of 321, 427 
Breast bone of birds .... 109 

Breathing center in developing 

embryo.481 

in grasshopper. 21 | 


to pages 


Breathing — continued 

in man . . 445 

not respiration. 5 

Brewing, scientific basis of . . 321 

Bromide of potassium . . . 503 

Bronchitis. 449 

Bronchus. 444 

Brook trout raised in hatcheries 78 
Brown creeper, at suet station 118 

food of.42, 114 

Brown hydra.160 

Brown rat. 135 

Browntail moths. 525 

Brussels sprouts, flowers of . . 217 

Bryophytes classified .... 9 

Bubbles of oxygen in masses of 

spirogyra. 306 

Bubonic plague, a bacterial 

disease. 489 

Bud, in reproduction of yeast 

plant. 322 

Budding cells of yeast 322 

Buds, a characteristic of stems 264 
Bugs, members of Hemiptera . 29 

Bullfrog, time required for 

development. 93 

Bullhead, organs of smell in 76 

Bumble bee, carrier of pollen . 45 

economic value of ... 45 

Burbot, a bony fish .... 79 

Burdock, common weed . . . 301 

distribution of seed by ani¬ 
mals .241 

Bureau of Chemistry . . 505, 526 

Bureau of Entomology . . . 525 

Bureau of Fisheries .... 526 

Bureau of Plant Industry . . 526 

Butcher bird (shrike) . . . . 112 

Butter, example of fat ... 416 

flavor of, due to bacteria . . 311 

indirect product of plants . 376 

value of as food.416 

Buttercup, characteristic mem¬ 
ber of crowfoot family . . 297 

Butterflies, classified ... 9, 29 

complete metamorphosis of . 28 

Butterfly, swallowtail, from cel¬ 
ery worm. 41 

larvae of. 41 

Buzzards, food of.116 

By-product of photosynthesis . 279 


































6 


INDEX 


C 

Cabbage, member of mustard 

family. 

yellows, a plant disease . 
Cabbages, storage of food in 
value of, as food .... 
Cactus, length of roots of 
Calcareous skeleton of coral 
Calcium, a chemical element 
Calcium phosphate, in Pasteur 

solution. 

Callus in broken bone . . . 

Calorie, defined. 

needs . 

Calyptrogen. 

Calyx, described. 

Cambium. 

Cambium layer in woody stems 
Camel, economic importance of 
Camomile, flowers of . . 
Canada thistle .... 
Canal, alimentary, of frog 
of man (digestive tube) 

Cancer. 

Cane sugar in Pasteur solution 
Canine teeth . . . 

Canker worms . 

Capillaries, described . 

Capillary circulation 

Caprifig. 

Capsule, a form of fruit 
dehiscent fruit . . 

of moss. 

Capsule containing eggs of 

earthworm. 

Caraway, member of parsley 

family. 

Carbohydrates, a class of food 

stored by bean. 

Carbolic acid, a disinfectant 

a poison -. 

Carbon. 

Carbon dioxide, a waste product 


of respiration . . . 5, 21, 446 

formed by yeast plant. . . 321 

product of respiration in 

seeds.229 

taken from the air by 

' plants.278 

Cardiac valve of stomach . . 408 


Care of the eyes.475 

Care of food.497 

Care of the teeth.406 

Care of young by fish .... 80 

Careless pruning, results of . . 358 

Carnivorous plants, modifica¬ 
tions of.366 

Carp.79 

Carpellate cone of pine . . . 343 

Carrier of disease.500 

Carrion beetle, beneficial insect 34 
Carrot, example of biennial. . 252 

member of parsley family . 300 

storage of food in ... 278 

Cartilage, in skeleton .... 433 

rings in air passages . . . 444 

where found.433 

Casein, a form of protein . 14, 416, 

505 

Castor oil.222 

Catalpa, as ornamental trees . 364 

rapid growth of.352 

Caterpillars, destructive insects 27 
larvae of butterflies .... 28 

stage in metamorphosis . . 28 

Catkin-like flowers of walnut . 297 

Catnip, a medicine.300 

Cattle, escape inspection 177, 500 

value of, to man.376 

Caudal fin of crayfish .... 61 

Caudal region of fish .... 72 

Cauliflower, use of .... 217 

Cause of disease.487 

Causes of obesity.504 

Caustic potash in Fehling’s solu¬ 
tion .228 

Cedar, a conifer.352 

Cedar of Lebanon, age of . . 261 

Cedar, leaves of.345 

Celery, plant blanching of . . 293 

storage of food in ... . 292 

Cell, name given by Hooke . . 141 

of pleurococcus.304 

unit of structure .... 6 

wall. 7 

Centipedes.66 

Central axis of pine cone . . 343 

Central cavity, of sponge. . . 156 

of bone . 436 

Central nervous system, of frog 88 
of man.468 


References are to pages 


298 
380 
292 
292 
254 
166 
13, 412 

322 
436 
416 
418 
247 
198 
267 
267 
134 
217 
261, 272 
86 
404 
488 
322 
406 
41 
453 
453 
243 
237 
. 237, 238 
328 


183 

300 

410 

228 

512 

221 

12 





























INDEX 


References 


Cephalopods, group of mollusks 191 

Cere.Ill 

Cereal foods, source of 295 

Cereal insect investigations . . 525 

list of ........ 295 

Cerebellum, of amphibians . . 89 

of child.481 

Cerebral ganglion of mollusk . 188 

Cerebral hemisphere of frog . 88 

Cerebrum of man.466 

Certified milk, defined . . . 315 

Cesspools, source of danger . . 519 

Chameleon, a lizard .... 101 

Chara, food of crayfish ... 62 

Characteristics, of birds . 107 

of man’s skeleton .... 434 

Cheese, cottage.505 

example of protein .... 419 

flavor of ....... 311 

indirect product of plants . 376 

Cheese skipper.54 

Chemical change, defined . . 10 

Chemical compounds .... 13 

Chemicals, used to enrich soil, 

“ fertilizers ”.394 

Chemical terms, explanation 


Chemical test for carbon dioxide 229 

Cherry, wood of.352 

Chest cavity of man .... 445 

Chestnut, member of beech 

family.297 

trees, value of.351 

Chickadee, at suet station . . 118 

destroyer of eggs and larvae 

of Lepidoptera . . . . 114 

food of.42,114 

Chickweed, viability of . 223 

Child Welfare movement 518, 537 
Chimney swifts, feet of . . . 108 

China, dependence on rice . . 296 

Chinch bug, harmful insect 17 

Chipping sparrow, useful bird . 114 

food of. 42 

Chloride of lime.512 

Chloroform, example of anes¬ 
thetic .480 

action on lipoid.480 

Chlorophyll, in cells of pleuro- 

coccus.305 

Cholera.514 


7 

are to pages 


Chorpid, coat of eye .... 473 

Cicada, description of... . 33 

Cigarette smoking, effect of . 485 

Cilia, in air passage .... 446 

of paramecium.146 

of sperms of moss, use of . . 329 

Ciliated larva, of liver fluke . . 176 

Circular muscles, of earthworm 176 
Circulation, a fundamental 

function. 5 

effect of alcohol on ... . 456 

in crayfish.64 

in plants.281 

of mollusks.187 

Clam, example of mollusk . 9, 185 

laboratory study of. . . . 187 

oversight of, by Bureau of 

Fisheries.526 

Clams, artificial raising of . . 193 

edible.192 

fresh water.185 

Clasping base, of grass leaves . 288 

Classes of bees.46 

Classification, basis of, in 

Protozoa.141 

of birds.110 

of fruits.237 

of seeds.227 

of living things. 8 

Clean milk.313 

Clear cutting in forests . . . 362 

Cleistogamous flowers, defined 204 

Clematis.297 

member of crowfoot family . 297 

use of petioles in .... 290 

Climbing plants, thigmotropism 

in.286 

Climbing stems compared with 

trees.260 

Clitellum of earthworm . . . 182 

Cloaca of frog.86 

Clothing, obtained from mallow 

family.299 

source of. 299, 376 

Clotting of blood.451 

Clover affected by darkness 291 
member of pulse (bean) 

family.299 

Club moss, related to ferns . . 333 

spores of.339 

uses of.339 






































8 


INDEX 


References are to pages 


Cluster cup stage of black stem 


rust.386 

Coal, formation of.339 

study of, in connection with 

ferns.339 

Coach or carriage horse . 129 

Coating of hairs, use to Arctic 

plants.283 

Coats of pollen grain .... 208 

Cobra, most deadly snake . 102 

Cocaine, a poison.487 

cause of disease.506 

Coccus, a form of bacteria . . 309 

Cocklebur, adaptations of . . 241 

Cockroaches, family of Orthop- 

tera.29 

Coconut, a fruit distributed 

by water.241 

Cocoon, of codling moth ... 27 

Cod, classified ...... 9 

example of bony fish ... 71 

value of, as food.423 

Codling moth, a harmful Lepi- 

doptera.43 

complete metamorphosis of . 27 

controlled by spraying . . 43 

description of.39 

destroyed by birds .... 42 

Ccelenterates, classified ... 8 

examples of.160 

described.160 ! 

Coelome of earthworm . . . 1801 

Coffee, effect on heart . . . 456 | 

Cold, a common disease . . . 448 

Cold-blooded animals .... 75 

Cold storage, purpose of . . . 243 

Coleoptera, examples of . 34 

order of insects.29 

Collar of grass leaf .... 288 

Collective fruit.239 

Colonial Protozoa.152 

Colony, hydroids.164 

Color of fungi, reason for . . 320 

Colors, use of, in flowers . . 199, 202 

Columbine, use of.297 

Communicable diseases . . . 488 

prevention of.489 

Comparison of monocotyledon- 
ous plants with dicoty¬ 
ledonous .267 

of pleurococcus and spirogyra 305 


Comparison — Continued 

of unicellular plants with 


multicellular.305 

Compass plant.291 

Complete flower, definition of, 199 

also perfect.199 

Complete metamorphosis of 

insects.27 

Complex flowers of higher 

plants. 207, 378 

Complexion, light, dark . . 459 

Complex systems of higher 

plants.378 

Composite Family.301 

Composite flowers.206 

Compound leaves, defined . . 277 

Conditions necessary for the 

growth of bacteria . 310 

for satisfactory water supply 498 
Conducting system, lack of, in 

algae.370 

Conducting tissue of pteris stem 334 
Conifers, general characteristics 341 

related forms of.345 

summary of.365 

Connective tissue, sheets of . . 435 

Conservation of energy ... 11 

Conservation of forests . 350 

Conservation of land .... 391 

Conservation of national re¬ 
sources .391 

Conservation of wild flowers . 394 

Consumption, treatment of . 491 

Contact, movement caused 291, 367, 

369 

Contagions.492 

Contractile vacuole of amoeba . 145 

Control of bacteria.313 

Cooper’s hawk, economic status 

of.115 

Copperhead snake.101 

Copper sulphate, in Fehling’s 

solution.228 

Coral.166 

Coral islands, formation of . . 166 

Coral reefs.166 

Corals, example of Coelenterata 8,160 

Cordage.262 

Core, in pome fruits .... 236 

Coriander, member of parsley 

family.300 






























INDEX 


9 


References are to pages 


Corn, distribution of ... 

296 

Crayfish — Continued 



embryo leaves of .... 

225 

circulatory system of . 


64 

example of monocotyledon . 

226 

digestive system of . . 


63 

flower, described .... 

204 

example of Crustacea . 


60 

indehiscent fruits .... 

237 

food and food-getting . 


62 

kernels filled by corn smut . 

324 

green glands of . . . 


63 

laboratory study of. 

226 

laboratory study of . . 


61 

leaf, description of ... . 

288 

life history of . 


64 

member of grass family . . 

295 

nervous system of . . 


64 

one of first plants culti- 


respiration of . 


63 

vated. 

295 

typical crustacean . 


60 

plant, prop roots of . . . 

253 

Creeping disk of snails . 


190 

raising as an industry . 

296 

Creeping stem, of trailing 

ar- 


raising as an industry, impor- 


butus. 


395 

tance of. 

296 

Crenate margins of mint leaves 

300 

“ seed, ” comparison with 


Creosote, preservative of woods 

354 

bean. 

224 

Cricket, member of Orthoptera 

29 

seedling. 

225 

harmful insect . . . . 


29 

smut, a parasite on corn . 

324 

Crocodiles, distribution of 


104 

smut, a fungus. 

324 

example of reptiles . . 


99 

stem. 

267 

Crop of earthworm . . . 


181 

Cornea of eye. 

473 

Cross-fertilization, defined . 


210 

Corolla, described. 

198 

changes produced by . 


211 

Corpuscles, red and white . 

449 

Cross-pollination, advantage 

of 

210 

Cortex of root. 

247 

effect upon wild plants 


211 

Cortical layer of kidney . . . 

458 

in breeding oats . . . , 


390 

of root. 

247 

Crow, example of birds . . 


9 

Corymb. 

214 

Crown, part of flower . 


202 

Cosmetic preparations 

504 

Crows, as scavengers . 


116 

Cottage cheese. 

505 

food of. 


36 

Cotton, member of mallow 


Crowfoot family, biting juice of 

297 

family. 

299 

characteristics of 


297 

source of clothing . . . 299, 376 

members cultivated for orna- 


Cottony cushion scale 

34 

ment. 


297 

Cotyledon of corn. 

225 

products of. 


297 

of bean. 

219 

Crustacea, classified . 


9 

of bean, importance of as 


economic importance of . 


65 

food. 

222 

Crustacea and related forms 


60 

of bean, storage of food in . 

220 

Cryptogams, classified . . 


9 

parts of seed. 

219 

defined. 


9 

Coughs . 

492 

Cuckoos, food of ... . 


42 

Cow, example of mammal 

9 

Culex (mosquito) . . . . 


55 

Cowbirds, nesting habits of . 

112 

Culture, for protozoa . 


143 

Cowpox, Jenner and .... 

510 

of bacteria. 


501 

Crabs, classified. 

9 

Curd of milk. 

416, 505 

common name for crayfish . 

60 

Cure of plant disease 


387 

economic importance of . 65, 526 

Cures of deafness .... 


503 

example of Crustacea . . . 

9 

Cures of epilepsy .... 


503 

Cranium of frog. 

88 

Cures of quacks .... 


501 

Crayfish, discussed. 

60 

Curing of meat, purpose . . 


313 

appendages of. 

601 

Curlydock, viability of . . 


223 































10 


INDEX 


References 


Curly maple.352 

Currant, example of berry . . 233 

Currant worms, caterpillars. . 28 

Cuticle of paramecium . . . 146 

Cutin of leaf.283 

Cuts, treatment of.455 

Cuttlefish, a cephalopod . . . 191 

compared with squid . . . 192 

Cutworms, harmful insect . . 41 

Cyclops, a small crustacean . . 65 

Cyme, form of inflorescence . 215 

Cypress trees, conifers 253, 352, 345 

Cypris.65 

Cytoplasm, of pleurococcus . . 305 

of amoeba.144 

of nerve cells.466 

of protoplasm. 7 


D 


Daddy-long-legs, an arachnid .' 66 

Dairy cow, discussed . . . . 131 

Daisy, a common weed . . . 301 

a composite.301 

Dandelion, a common weed . 301 

a composite.301 

Daphnia.65 

Darkness, effect of, on clover 

and oxalis.291 

Dead matter simplified by bac¬ 
teria .310 

Deafness, “ cures ” .... 503 

Death caused by insects ... 29 

Deaths among infants . . . 513 

Deaths from communicable 

diseases.497 

Decay, caused by bacteria . . 310 

Deciduous leaves, defined . . 283 

Decomposition caused by bac¬ 
teria .310 

Defects in hearing.476 

Definite annual growth . . . 265 

Definitions of common biologi¬ 
cal terms.1-8 

Dehiscent fruits, defined. . . 237 

forms of.237 

Deliquescent stems . . . 265,341 

Denuded hills, cause of 

freshets. 349, 350 

Deodorizers, not disinfectants . 512 


are to pages 

Department of Agriculture of 
United States, inspecting 


meat.500 

investigations concerning cot¬ 
tony cushion scale ... 34 

Dependence, of fungi .... 320 

of mistletoe.369 

Dermatogen.247 

Dermis, defined.459 

Desert plants, living conditions 371 
Deserts, habitat of plants . . 371 

Determinate inflorescence . . 216 

Development of amphibians . 90 

Development of tadpole . . 91, 92 

Devices for regulating trans¬ 
piration .283 

Devil’s paint brush, a weed . . 272 

Dew, use by sperms of mosses . 329 

Diamond-shaped markings of 

marchantia.331 

Diaphragm, of man .... 408 

characteristic of mammals . 445 

passage of oesophagus 

through.408 

Diastase, enzyme of fermenta¬ 
tion .. . 281 

Dicotyledons, group of plants 9, 227 
represented by bean, squash, 

etc.226 

seeds of.227 

Diet.418,410 

Digestion, a life process ... 5 

completed in intestine . . . 412. 

described.411 

effect of alcohol on ... 430 

in leaves of Venus’s flytrap . 367 

in plants.281 

laboratory study of. . . . 413 

of food by pleurococcus . . 305 

of food in leaf.281 

of food in seed.229 

of starfish.171 

Digestive fluids, of man . .411, 412 

Digestive organs, of crayfish 63 

of frog.85 

of man, summary of ... 431 

Digestive system of animals, 

student report on . . . 413 

Digestive system of clam . . 187 

Dill, member of parsley family 300 
Dioecious flower, defined . . 204 
































INDEX 


11 


References 


Diphtheria (germ disease) . 448, 489 

antitoxin. 449 

carriers.500 

ten years of in France . . . 511 

treatment of .... . 507, 511 

Diptera (order of insects) . . 29 

described.29,54 

Dirty milk, bacteria in ... 313 

Disk flowers.206 

Disease, cause of.487 

of plants, necessity for 
knowing . . . . . . 380 

of respiratory tract .... 448 

results of. 514 

student report on ... . 487 

summary of. 495 

Diseases, cause'd by abnormal 

growth of tissues .... 487 

caused by bacteria .... 488 

caused by plants or animals . 488 

caused by poisons, list of . . 487 

of respiratory tract .... 448 

Disinfectants. 507, 512 

Disinfection.512 

Disk, central, of starfish . . . 169 

adhesive, of starfish . . . 171 

Disk-flowers of composites . . 206 

Dispersal of seeds, agencies for 240 

by animals.241 

by pappus and hooks . . . 241 

by water.241 

by wind.241 

necessity for.240 

Disposal of sewage .... 461 

Dissected leaves of crowfoot 

family.297 

Dividing cells of pleurococcus . 305 

Dividing egg, becoming tadpole 91 

of frog.91 

Division of Drugs.505 

Division of labor .... 153, 154 

in sponge.155 

in volvox.153 

Division of Publications, 

W ashington . 526 

Dodder.290 

Dog.: . . 134 

Domestic fowl, wings of . . . 108 

Dormancy in seeds .... 223 

Dorsal blood vessel of earth¬ 
worm .182 


to pages 


Dorsal surface of earthworm 179 
Double flowers defined . 204 

Dough in bread making . . . 427 

Down on wind-distributed 

seeds.241 

Downy mildew. 531 

Downy woodpecker, a per¬ 
manent resident . . . Ill 

food of. 114 

Dragon flies, enemies of mos¬ 
quito . 56 

member of Odonata ... 29 

Dressed lumber, defined. . . 363 

Drills, a method of planting 376 

Drones (bees) ..46 

Drowning, a form of suffoca¬ 
tion . 447 

Drupe, defined.237 

Dry farming. 391 

Dry fruits, bean an example of 237 
Drying, protection of bacteria 

from.. 311 

Drying fruit, purpose of . . . 313 

Dry season, effect of, on annual 

ring.266 

Dry seasons, effect of, on size 

of cells.266 

Ducks, feet of.108 

Duration of roots.252 

of stems.261 

E 

Eagle, a scavenger.116 

claws of.108 

wings of.107 

Ear, organ of sound .... 476 

balancing organ. 475 

membrane of frog .... 83 

of grasshopper.24 

pistillate flower of corn . . 204 

sense organ. 475 

wax in.476 

Earliest homes of man . 400 

Earthworm, discussed .... 178 

economic importance of . . 183 

example of worms .... 9 

excretions of.180 

illustration of true worms . 178 

laboratory study of . . . 180, 182 

life history of.182 





























12 


INDEX 


References are to pages 


Earthworms — Continued 


Egg nucleus. 


209 

locomotion of. 

179 

Egg-plant, a food plant 

of 


respiration of. 

180 

nightshade family . 


301 

ventral surface. 

179 

a fruit. 


245 

Echinodermata, classified . . 

8 

Eggs, of frogs. 


91 

Echinoderms, discussed . . . 

169 

of grasshopper . 


25 

Economic importance, of algae . 

307 

of moss plant. 


329 

of amphibians. 

97 

Elder, use of flowers of . 


217 

of birds. 

114 

Elements and compounds 


12 

of ccelenterates. 

167 

Elm tree, roots of ... 


364 

of crustaceans. 

65 

wood, characteristics of . 


352 

of echinoderm group 

173 

Embryo, corn, position of 


225 

of earthworms. 

183 

growth of, in ovule . 


219 

of fern group. 

339 

heart of. 


480 

of flowers. 

216 

of coelenterate .... 


165 

of gymnosperms. 

346 

of coral . 


167 

of leaves. 

292 

of liver fluke. 


176 

• of lichens. 

326 

parts of. 


219 

of mammals. 

134 

sac, contents of . 


219 

of mollusks. 

192 

vigorous, result of cross-pol- 


of mosses. 


lination. 


211 

of paramecium. 

149 

Employment afforded by plant 


of plants. 

375 

industries. 


376 

of roots. 

255 

Enamel, effect of bacteria on 


407 

of seeds. 

222 

Encystment of amoeba 


145 

of sponges. 

157 

Endoderm, of sponge . 


155 

of starfish group. 

173 

Endoplasm. 


144 

Economic insects. 

29 

Endosperm, food supply 

of 


Economic interest in plants . 

375 

corn. 


225 

Economic phases of grasshopper 

29 

of corn grain. 


225 

Economic point of view in study 


of corn, used for growth 

of 


of plants. 

375 

seedling. 


227 

Economic value of mosses . 

330 

Enemies, of frog .... 


84 

Ectoderm, of sponge .... 

156 

of insects. 


34 

of hydra. 

160 

oflepidoptera .... 


41 

Edible clams, names of 

192 

of man. 

134,137 

Edible fats. 

14 

Energy, defined. 


10 

Edible mollusks, list of . . . 

192 

uses of in body .... 


418 

Edible pulp of plum, factor in 


English sparrow, destroys 


distribution. 

241 

weevils. 


35 

Eels, migrations of .... 

77 

eats larvae of Lepidoptera 


42 

Effect, of alcohol on digestion 

430 

permanent resident . 


111 

of drugs and alcohol 

456 

scientific name of . . . 


10 

Efferent fibers. 

470 

English walnut, protein in . 


410 

Efficiency centers of brain . 

481 

Enlarged base of onions, stor- 


Egg, a reproductive cell . . . 

153 

age of food in ... . 


286 

white of, example of protein 

416 

Enriching the soil by nitrogen . 

256 

Egg-capsule of earthworm . . 

182 

Environment, defined . . 


10 

Egg cell, of frogs. 

90 

discussed. 


536 

fertilization of, in plants . 

213 

illustrated by development of 


volvox. 

153 

frog. 


97 













































INDEX 13 


References are to pages 


Enzymes. 

14, 412 

Exercise, benefits of . . 


447 

of yeast plant . . . 

. 321 

necessary to keep one fit 


440 

secreted by bacteria 

. 311 

value of. 


440 

Ephemeridae, an order of 

in- 

Exercising, out-of-doors . 


447 

sects . 

29 

to keep well .... 


447 

Epidemic, defined . 

. 515 

Exhalent pores .... 


156 

Epidemics, after wars . . 

. 514 

Exhalent siphon of clam . 


185 

of diseases, costliness of 

. 514 

Exoskeleton, of crayfish . 


60 

sore throat . . . 

. 499 

of grasshopper . . . 


25 

Epidermal tissue of pteris stem 334 

Experiment, to show production 


Epidermis, of root . . . 

. 247 

of carbonic acid in plants 

280 

of leaf .... 


performed on plants . . 

229,280 

of rootlets. 

. 248 

stations. 


377 

of xerophytes, character 

of 371 

Expiration, defined. . . . 


445 

outer layer of skin . . 

. 459 

Explosion of fruit case 

to 


Epiglottis. 

. 444 

scatter seeds . . . . 

237 

r , 238 

Epiphytes, definition of . 

253, 373 

Extent, of original forest. 


348 

habitat of. 

. 373 

of root system .... 


252 

Epsom salts in cosmetics 

. 504 

External appearance of woody 


Equisetum. 

. 338 

stems 


264 

Erosion checked by roots 

. 256 

External parts of fish . 


71 

Eskimo, diet of ... 

15 

Extinct animals, remains of . 


95 

surroundings of . 

97 

Eye . 


472 

Esophagus, of crayfish 

. 63 

Eyeball. 


472 

of earthworm .... 

. 181 

Eyelid. 


472 

of frog. 

. 85 

Eyes, of fish. 


75 

of man. 

. 408 

of grasshopper .... 


22 

Essential parts of flower . 

199,201 

of man. 


472 

Ether, an anesthetic . 

. 480 

of man, care of ... 


475 

test for oil. 

. 228 

of Nereis. 


184 

Eustachian tube, of frog . 

. 83 

of vertebrates .... 


70 

of man. 

. 406 




Evaporation of perspiration 

ef- 

F 



feet of .... . 

. 459 




Evening grosbeak, winter vis- 

Faeces, removal of . 


415 

itant .... 

. 112 

Fainting, cause of ... 


456 

Evergreen, leaves defined 

. 341 

False blossoms. 


243 

trees, examples of . 

. 345 

Fangs of rattlesnake . . . 


101 

Evergreens, characteristics o 

. 341 

Farmers’ Bulletins .... 


526 

Examples of plant societies 

. 370 

Fascicled roots. 


251 

Excelsior, source of 

. 352 

Fatigue of muscles 


439 

Excretion, a life process . 

5 

Fats, a class of foods . 


410 

definition of ... 

5 

absorption of. 


414 

in crayfish. 

. 63 

furnished by animals . 


416 

in grasshopper 

. 25 

nutrients. 


13 

in plants. 

. 282 

Fear of snakes. 


102 

of hydra. 

. 163 

Feathers, a characteristic i 

of 


of man. 

. 443 

birds. 


110 

of mollusks .... 

. 188 

of birds, modifications < 

of 


Excurrent stem of ever- 

skin. 


459 

greens. 

265, 341 

Federal Plant Quarantine Act 


522 
















































14 


INDEX 


References are to pages 


Feeble-mindedness ... 

536 

Fins, of fish. 

. 71, 72 

Feelers, of bullhead .... 

76 

use of, in balancing 

and 


of grasshopper. 

22 

steering. 


72 

Feet of birds, different kinds 


Fires, forests destroyed by 

357. 

, 359 

of. 

108 

prevention of, by national 


Fehling’s solution, formula . 

228 

government 


358 

test for sugar. 

228 

Fireweed in plant succession 

375 

Female strobilus of pine . . 

343 

Firewood, furnished by beech 


Femur, of grasshopper 

24 

family. 


297 

Fennel, member of parsley 


Fireworks, use of spores of club 


family. 

300 

moss in. 


339 

Ferment. 

412 

Firs, conifers. 


345 

Fermentation, cause of . . . 

321 

Fish, care of young 


80 

effect of . 

321 

production .... 


423 

produced by enzymes . 

311 

spawning habits . 


76 

Fern, gametophyte .... 

336 

substitute for meat . 


423 

Fern group, plants belonging to 

333 

summary of ... 


81 

Ferns, example of pterido- 


Fish hatcheries .... 


77 

phytes. 

9 

Fishes, bony. 

. 70, 71 

field study of. 

337 

circulation of . 


75 

habitat of. 

333 

classified. 


9 

laboratory study of. . . . 

337 

food-taking .... 


73 

Ferns and their allies . . 

333 

reproduction of . 


76 

in relation to water .... 

333 

respiration of . . . . 


74 

summary of . ' . 

340 

scales of. 


72 

Fertilization, defined . 91, 165, 

211 

special senses of . 


75 

of egg cell in the ovule . . 

212 

with lungs. 


70 

Fertilized egg cell, beginning 


Fish fry, young .... 


78 

of new organism .... 

153 

yolk, food for. . . . 


76 

of volvox. 

153 

Fission, a form of cell division 

305 

Fertilizers, use of, to supply 


Flaccid cells. 


283 

elements. 

394 

Flagella. 


152 

Fibers in blood. 

451 

Flagellata, group' of Protozoa . 

149 

Fibrinogen, in formation of clot 

451 

Flat worms, classified . . 

• 9, 

175 

Fibrous roots. 

251 

Flavor, of butter . . . 


311 

Fibrovascular bundles, cells of 

266 

Flavors, caused by fermentation 

311 

conducting vessels .... 

248 

by bacteria .... 


311 

in leaves. 

287 

Flax, family. 


299 

structure of. 

266 

useless parts of plant 

re- 


use of, in photosynthesis . 

281 

moved by bacteria . 


311 

Field study, of ferns .... 

337 

Fleas, member of Siphonaptera 

27 

of gymnosperms. 

345 

Flesh-eating animals . 


137 

of insects. 

19 

Fleshy fruits. 

237, 

239 

of moths and butterflies . 

44 

Flicker at suet station 


118 

Field suggestions, mammals 

140 

Flies, carriers of bacteria 


29 

Fig-raising in the U. S. . 

243 

classified. 

. . 9, 29 

Filaments, of gill. 

73 

members of Diptera 


29 

of anthers . 

198 

Flipper of seal .... 


126 

Filtration plants. 

462 

Floods, cause of ... 

348, 351 

Finches, beak of. 

109 

prevention of . 


351 

Finger prints. 

536 

Flour, food elements in . 


426 













































INDEX 


15 


References are to pages 


Flower, defined . . . . 

202 

Forestry, defined . . . . 


346 

Flower bud. 

198 

Forests, extent of, in U. S. . 


348 

Flowering plants . . . .. . 

295 

importance of .... 


347 

common families .... 

295 

patrolling. 


360 

summary of .. 

302 

proportion necessary . . 


348 

Flowerless plants, classification 


Formaldehyde, disinfectant. 


512 

of ... .. 

9 

a preservative .... 


314 

Flowers, home work . . 208, 

217 

gas. 


512 

of lilies. 

199 

Formalin, in milk .... 


428 

of nasturtium. 

198 

Formation of coal and peat . 


339 

wind-pollinated. 

210 

Forms of leaves .... 


277 

Flycatchers, eaters of larvae . 

43 

Fossils, described .... 


95 

food of. 

115 

shells of animals now extinct 

95 

Flying wings of grasshopper 

23 

Foul breath caused by bacteria 

407 

Foliage, rank-scented leaves of 


Fox sparrows, transients . 


112 

nightshade family 

301 

Fox terrier, comparison 

of 


Food, care of. 

497 

primitive horse with . 


128 

definition of. 

410 

Frecldes. 


504 

first plants to be cultivated 


Freezing, protection of bacteria 


for, list of. 

296 

from. 


311 

for reindeer in Arctics . . . 

330 

Fresh air, a condition for health 

447 

fungi, a source of ... 

324 

aid in curing consumption 


491 

necessary to keep one fit 440, 497 

Freshets, cause of ... 


348 

of animals, student report 


prevention of .... 


351 

on. 

411 

Fresh-water planarians . . 


175 

of bacteria. 

310 

Frog, bull, development of . 


93 

of clam. 

188 

central nervous system of 


88 

of frogs. 

84 

common. 


83 

of muscles. 

439 

description of. 


83 

of plants, study of ... . 

281 

eggs. 


90 

of snakes. 

101 

example of amphibians 


9 

of starfish — how taken . 

171 

enemies of. 


84 

storage. 228, 

, 229 

fangs of. 


101 

stored in cotyledons of bean . 

220 

food of. 


84 

Food and Drugs Act .... 

502 

green, development of . 


93 

Food-getting, by grasshopper . 

21 

habitat of. 


83 

by starfish. 

171 

internal organs of . . . 


85 

Foods . 

410 

laboratory study of . . . 

89, 83 

Food shortage. 

422 

leopard, description of . 


83 

Foodstuffs in bean. 

228 

reproduction of frog 

87, 90 

Food substitutes. 

421 

respiration of. 


84 

Food taking, of earthworm . 

180 

Fronds of pteris 


333 

Food vacuole of amoeba . 

144 

Fruit, defined. 


233 

Foot of clam. 

186 

flies. 


522 

Foot of moss sporophyte . 

330 

of bean . 


237 

Forage insect investigation 

525 

of pine. 


344 

Fore limbs of animals dis¬ 


of poppy. 


238 

cussed . 

126 

production in connection with 


Forest products. 

351 

storage roots .... 


256 

rangers, work of. 

358 

steps in development of . 


233 

Forest reserves. 

361 

use of, to plant . . . ■ . 


234 














































16 


INDEX 


References are to pages 


Fruit packers’ care not to break 

skin of fruit.243 

Fruits, distributed by animals . 241 

by wind.241 

distributers of seeds . 239, 241 

effect of cross-pollination on . 377 

furnish luxuries of food . . 244 

of rose family.298 

with hooks.241 

Fruits and seeds.245 

Fry.78 

Fucus vesiculosus.504 

Fuel, hardwood trees, source of 297‘ 

Fumigants.507 

Fundamental functions, dis¬ 
cussed .4,5 

Fundamental tastes . . .. 405 

Fundamental tissue of pteris 

stem.334 

Fungi, action in changing lava 

to soil.375 

as food.324 

classified. 9 

conditions favorable for 

growth.323 

summary of.326 

Fungus, an enemy of corn . . 324 

Furniture, lumber for .... 352 

Furs, as clothing.134 

Fusarium conglutinans, cause 

of cabbage yellows . . . 381 

% 

G 

Gall bladder of frog .... 86 

Gall flies, example of Hymen- 

optera.29 

Gallinules, toes of.121 

Game laws, purpose of . . . 395 

Gametes, defined.307 

of moss.329 

Gametophyte or sexual genera¬ 
tion of moss.329 

Ganglia, of clam.188 

of earthworm.181 

of grasshopper.25 

Garbage.519 

Garden slug, shell of ... 190 

Garden vegetables, belonging 

to mustard family . . . 298 

to parsley family .... 300 


Gas, a form of matter ... 10 

use in bread making . . . 427 

Gastric glands.409 

Gastric juice.412 

Gastric mill, of crayfish ... 63 

Geese, feet of.108 

wild, transients.112 

Gelatinous secretion of earth¬ 
worm .182 

Geotropism, defined .... 286 

Geranium slip, roots of . 379 

Germ, a name for unicellular 

organisms.309 

diseases........ 488 

in ice ..498 

G ermination, laboratory study of 227 

Germs.309 

a name for bacteria . . . 309 

getting well.491 

of disease carried by insects . 29 

Gila monster, poisonous lizard . 101 

Gill, cover.71 

Gill rakers.74 

Gill scoop, of crayfish .... 63 

Gill slits.69 

Gills, of fish.69, 74 

of clam.188 

of crayfish.63 

Ginger root, use of.256 

Girdle, pectoral.69 

pelvic.70 

Gizzard of earthworm . . . 181 

Glacial period, effect on man . 400 

Gland of starfish.170 

Glands, defined.409 

Glandular hairs of sundew . 361 

Glassy sponge, skeleton of . . 158 

Glomerulus of kidney 458 

Glucose. 14, 439 

Gluten.416 

Glycerin formed by zymase 427 
Glycogen, stored in liver 414, 439 
Gnats, eaten by birds. . . . 115 

Goats, economic importance of 133 
Goldenrod, a common weed . 301 

Goldfinch at feeding station 119 
Goldfish, a typical bony fish . 71 

killed by tobacco smoke . . 485 

Gonium.152 

Good food, value of, in cure for 

tuberculosis.491 













































INDEX 17 



References 

are to pages 


Gophers, harmful mammals 


134 

Guard cells, of stomata . 

285 

Government inspection, 


of 


Guide to amount of food 

429 

meat. 


177, 

495 

Gullet, of paramecium . . . 

147 

of oyster beds . . . 



193 

Gulls, sailing birds. . . . . 

108 

Grafting, effect of . . . 



377 

Gums, effect of tartar on 

407 

discussed. 



270 

Gunpowder, use of willow char¬ 


Grain, differs from bean . 



224 

coal for. 

352 

of corn, a form of fruit 



237 

Guttation, defined. 

284 

“ Grain ” of wood . . . 


266, 

355 

Gymnosperms, by-products of . 

346 

Grains (cereals) 



244 

classified. 

9 

Grantia, classified . . . 



8 

discussed. 

341 

described. 



155 

economic importance of . 

346 

Grape sugar. 



439 

economic value of ... 

346 

Grass family. 



295 

field study of. 

345 

compared with rose family 


376 

in coal beds. 

339 

Grass, monocotyledon 



227 

reason for name. 

344 

wind-pollinated flower . 



210 

student report on ... . 

346 

Grasses, adaptations of . 



288 

Gypsy moths, injurious insects 


importance of, as food . 


296, 

376 

39, 525 

in plant succession . 



375 



Grasshopper, classified 


. 9, 29 

H 


classification of. 



28 



described . . . . . 



17 

Habitat, of evergreens 

344 

hairworm in body of . 



178 

of frogs. 

83 

laboratory study of . 



20 

of mosses. 

328 

life history of . 



25 

of protozoa. 

142 

mouth parts of . 



22 

Habits, as to alcoholic bever¬ 


parts of. 



22 

ages . 

478 

representative animal . 



18 

of plants, of interest to farmer 

376 

structure of ... 



22 

Haemoglobin in corpuscles . 

449 

Gravity, influence of, on roots . 

250 

Hair, origin of. 

459 

Gray substance of nerves 



468 

Hair snakes. 

177 

Great northern shrike, winter 


Hair worm. 

177 

visitant. 



112 

Hairs on leaves of Venus’s fly¬ 


Green algae. 



304 

trap . 

367 

Green frogs, development of 


93 

Hard maple as shade tree 

364 

Green glands of crayfish . 



63 

Hard palate. 

406 

Green manure .... 



257 

Hard wood of maple .... 

352 

Green manuring . . . 



257 

Harmful bacteria. 

309 

Green pea,s as food . . 



222 

Harvestman, harmless arach¬ 


Green turtles .... 



100 

nid . 

66 

Greyfish . 



80 

Haustoria, modified roots . . 

253 

Gristle, defined .... 



433 

Hawk, Cooper’s, harmful . . 

115 

Grosbeaks, beak of 



109 

example of bird. 

9 

Ground birds, wings of . 



108 

marsh. 

115 

Ground squirrels 



526 

red-shouldered. 

115 

Grouse . 



117 

red-tailed. 

115 

Growth of bean embryo . 



220 

sharp-shinned. 

115 

of nervous system . 



468 

Hawks, beneficial birds among 

115 

of stems. 



265 

claws of . ... ^ . . 

108 

Grubs, larvae of beetles . 



28 1 

Hawkweed, a common weed 

301 










































18 


INDEX 


References are to pages 


Hay infusion for protozoa 

143 

Hinge ligament of clam . 


186 

Head, cluster of flowers . . . 

214 

Hinge of clam .... 


186 

of grasshopper. 

22 

Hinge teeth of clam 


187 

Headache medicines .... 

507 

Hip bones of man . 


434 

Head end of earthworm . 

179 

Hogs, inspection of 

177, 500 

Heads, inflorescence of com- 


Hollow bones of birds 


109 

posite family. 

206 

Hollow stem, of horsetail 


338 

of a bone. 

436 

of parsley family 


300 

Head-thorax region of crayfish 

60 

Holly, use of wood of . 


352 

Health. 

487 

Hollyhock, member of mallow 


laws. 

464 

family. 


299 

Healthy bodies and bacteria 

316 

Home making, work of women 

426 

Hearing. 

475 

Home study of moths 

and 


Heart, of man. 

451 

butterflies .... 


44 

center. 

481 

Honey, amount of carbohydrate 


muscle cells. 

437 

in. 


410 

of crayfish . . . . 

64 

value of, in U. S. . . 


49 

valves of. 

452 

Honey-bee, discussed . 


45 

Heart and blood-vessels of 


development .... 


46 

man. 452, 453 i 

worker, queen, drone . 


46 

Heartwood. 

353 

Honey-bees clustering 

at 


Heat and pressure, influence 


swarming^ time , . 


48 

of, in forming coal . . . 

339 

Hoofs of cattle, origin of . 


459 

Heating, common methods of 

447 

Hooks, on fruit of burdock 


241 

milk, effect on bacteria . . 

314 

on fruits, use of . . : 


241 

protection of bacteria from . 

311 

Hookworm disease . . 


494 

Heel of man. 

434 

Hop lice destroyed by lady-bugs 

34 

Heliotropism, defined .... 

286 

Horehound, a medicine . 


300 

Hellebore, source of ... 

297 

Horned toad, a lizard . 


101 

Helpful bacteria. 

311 

Horns of cattle, origin of 


459 

Hemiptera, discussed .... 

58 

Horse, classified 


9 

order of insects. 

29 

discussed. 


129 

Hemlock, bark, use of 

346 

evolution of ... 


126 

conifer.. 

345 

use of. 


126 

Herbaceous plants. 

261 

Horse-chestnut, as shade tree . 

364 

Heredity, discussed . . .96, 532 

compound leaves of 


277 

of disease. 

516 

Horse-radish, member of mus- 


Hermit crabs, economic impor¬ 


tard family.... 


298 

tance of. 

65 

Horsetail. 


337 

Herons, beak of. 

109 

joints of stem 


338 

Herring, economic importance 


Horsetails, members of 

fern 


of. 

71 

group. 


333 

Hibernation, defined .... 

84 

related to ferns . 


333 

study of. 

140 

scouring rush .... 



Hickories, members of walnut 


Host, defined .... 


41 

family. 


of liver fluke .... 


176 

source of nuts. 

351 

Hotels, examination of hell 

> for, 

501 

wood, uses of. 

352 

House-fly. 

. 54. 57 

Hills, a method of planting . 

376 

killed by fungus . 


323 

Hilum of bean. 

219 

House-sparrow, scientific name 


Hinge joint. 

435 

for. 


10 









































INDEX 19 


References < 

are to pages 



Houses, source of materials for 

261 

Immovable joints . 


434 

How fertilization is accom- 


Immunity 



plished. 

212 

defined and discussed . 

. 

516 

How tracts can be reforested . 

356 

Immunization .... 


513 

How the smoker’s heart is 


Imperfect flowers, kinds . 


204 

affected. 

482 

of corn. 


204 

Howard, Dr. L. 0. 

525 

Importance of muscles 


437 

Human biology. 

399 

Importation of certain fruits for- 


Human progress. 

521 

bidden. 


524 

Humming birds, beak of . . . 

109 

Improving the varieties 

of 


summer residents .... 

112 

plants and animals . 


424 

Humor, aqueous. 

473 

Incisor teeth. 


406 

vitreous. 

473 

Incomplete flower, part lacking 


Humus, formed by leaf decay . 

351 

in. 


203 

Hybrids. 

243 

Incomplete metamorphosis 


26 

Hydra, cell layers in ... 

160 

Increasing the food supply 


423 

described. 

160 

Incurrent siphon of clam 


191 

example of coelenterate 

160 

Indefinite annual growth 


265 

laboratory study of. 

164 

Indehiscent fruits, defined 


237 

Hydra-like animals, described . 

164 

Independent existence of moss 


summary of. 

167 

gametophyte 


330 

Hydrastis, source of ... 

297 

Indeterminate inflorescence 


216 

Hydrochloric acid in artificial 


India, dependence on rice 

. 

296 

gastric acid. 

413 

Indian, environment of . 


97 

Hydrogen, proportion of, in 


Indian pipe. 

290, 369 

plants and animals . 

13 

Indigestion. 


429 

Hydroids, described .... 

164 

causes of. 


429 

examples of ccelenterates . 

160 

disguised by alcohol 


430 

Hydrophytes, definition of . . 

370 

tablets for. 


430 

finely-divided leaves of sub¬ 


Indistinct ring, left by 1 

bud 


merged forms. 

370 

scales. 


264 

Hydrotropism, defined . . . 

286 

Inflorescence .... 


213 

in roots . 

862 

Influence of alcohol on develop- 


Hymenoptera, discussed . . . 

45 

ment of brain . 


481 

order of insects. 

29 

Influences affecting the growth 


Hyphse of bread mold 

323 

of plants .... 


286 

Hypocotyl, part of embryo . 

220 

Influenza. 

492, 493 

part to grow first .... 

220 

Infusoria. 


149 

use of, to embryo .... 

220 

Inhalent pores .... 


156 

Hypopharynx of grasshopper 

23 

Inhalers. 


484 



Inherited diseases ... 


487 

I 


Inner chamber of eye . . 


473 



Inner coat of pollen grain 


208 

Ice, a form of water .... 

10 

Inner ear. 


475 

use of, in caring for milk . 

314 

Inoculation 


258 

Ice cream, dangers from . 

316 

Inorganic foods. 


412 

Ichneumones, discussed . 

41 

Inorganic matter 


10 

enemy of Lepidoptera . . . 

41 

Insanity. 


487 

members of order Hymenop- 


Insect, group, divisions of 

. 

28 

tera. 

45 

pollination. 


210 

Imbecility. 487, 536 

Insecta . 


9 

































20 


INDEX 


References 


Insect enemies of forests . . 358 

Insects, affecting the health of 

domestic animals.... 525 

affecting the health of man . 525 

affecting the health of shade 

trees.525 

carriers of bacteria .... 229 

devices of flowers for attract¬ 
ing .202 

examples of Arthropoda . . 9 

field study of.19 

object in visiting flowers . . 208 

pests.52 

Inspection of meat. . . 177, 500 

Inspiration, defined .... 445 

Insulation of nerve fibers . . 480 

Integument, of bean .... 219 

of ovules.212 

Intercellular spaces . 291, 454 

Internal, gills.92 

organs of frog.85 

lungs.92 

structure of earthworms, 

laboratory study of . . 182 

Intestinal glands.409 

Intestine .408 

Invertebrates, group of animals 8 

Inverted image.474 

Involuntary muscles .... 437 

Iodine test for starch .... 228 

Iris of eye.473 

Iron in blood cells.413 

proportion of, in living things 13 
Irregular flower of violet 204 

Irregular flowers, defined . . 204 

Irritability a fundamental func¬ 
tion .5,6 

Ivy, roots of.252 

Japanese barberry, immunity 

of.388 

Jaw bones of fish.71 

Jaw of man.406 

Jellyfish, example of coelenter- 

ate. 8 

members of hydra group . . 160 

Jenner, vaccination .... 510 

Jewelweed, explosive fruit of 238, 241 
Jimson weed, member of night¬ 
shade family.300 

Joints in man.434 


are to pages 


Juice of mustard family, char¬ 
acteristics of.298 

Juice of the buttercup, char¬ 
acteristics of.297 

Junco. 

at seed station.118 

at suet station.118 


K 


Katydids, a family of Orthop- 

tera.29 

Keel of bird’s breastbone 109 

Keeled sternum of bird . 109 

Keeping well.499 

Kelp, use of.504 

Kernel, comparison with bean 

pod.224 

Kidney, described.458 

Kidneys of frog.87 

Kidneys of man.458 

Kinds of foodstuffs in seeds 228 
Kinds of land used for forests . 356 

King bird.115 

food of.115 

Kingfisher, nesting habits of . 112 

Knees of cypress . . 252, 253 

Koch, discoverer of Bacillus 

tuberculosis.489 

of tuberculosis test .... 316 

study of bacteria by . 316, 489 

L 

Labium.22 

Laboratory experiments with 

leaves.286 

Laboratory study, of bacteria . 312 

of bean seed.227 

of bread mold.325 

of corn.226 

of ferns.337 

of foodstuffs in seeds . . . 228 

of fruits.234 

of grasshopper.20 

of gymnosperms.346 

of leaves for storage . . . 379 

of lily.200 

of live fish.72 

of marchantia.331 































INDEX 


21 


References are to pages 


Laboratory study — Continued 


Leaves, arrangement of . 


289 

of moss ........ 

330 

of elms. 


289 

of moth and butterflies . . 

44 

of ferns. 


333 

of nasturtium. 

196 

of grass, shape of 


295 

of pleurococcus. 

305- 

of mosses. 


329 

of protozoa. 

146 

of pine, described . . 


343 

of reptiles. 

106 

of pitcher plant . 


366 

of roots. 

249 

of trees, arrangement of 


289 

of skeleton. 

436 

used for food .... 


292 

of spirogyra. 

307 

used for medicine . 

. . 

292 

of sponge. 

156 

Leaves of beech 


297 

of starfish ....... 

170 

Leech . 


175 

of stems. 

263 

Leeuwenhoek, improver of 

mi- 


of tasting. 

405 

croscope. 


316 

of twigs. 

264 

Legs and wings of birds . 

107, 

108 

of worms. 

180 

Lens of eye ..... 


473 

of yeast plant. 

322 

Lenticels, described . . 


265 

Labrum. 

22 

Leopard frog. 


83 

Lacteals. 

414 

Lepidoptera. 

. 29, 39 

Lactic acid, effect of ... 

314 

Lice. 

. 57, 514 

Ladd, Dr. E. F., quoted . 

506 

Lichens, described . 


325 

La grippe. 

493 

Lichens, action in changing 


Ladybug . 

34 

lava to soil .... 


375 

larvse of.. . 

34 

discussed. 


325 

Ladyslipper. 

396 

epiphytic habit of . 


373 

Lake trout raised in hatcheries 

78 

field study of ... . 


326 

Lampreys. 

, 70 

Life cycle of plants 


221 

Land snail. 

190 

Life history, of ant 


52 

Larch, a conifer. 

345 

of clam. 


188 

use of wood of. 

352 

of eel. 


77 

Large cells, position of, in an¬ 


of fern. 


334 

nual ring .... 

266 

of grasshopper 


25 

Large intestine. 

408 

of house-fly .... 


56 

Lark, meadow, nest of 

J12 

of mosses ..... 


330 

Larkspur, medicinal plant . 

297 

of monarch-butterfly . 


36 

Larva . 

27 

of plant, defined . . . 


221 

Larynx of man. 

445 

of potato-beetle . 


35 

voice box. 

445 

of reptiles. 


99 

Lateral bud. 

264 

of toad. 


93 

Lava, change to soil .... 

375 

Life of flowering plants . 


195 

Layering. 

271 

Life preservers from balsa wood 

356 

Lead, cause of disease . . 

487 

Life processes, of grasshopper . 

19 

Leaf. 

274 

of bacteria. 


310 

of oak. 

297 

Ligaments. 


435 

scars, defined. 

264 

Lily family. 


297 

Leafless plants. 

290 

Lily flower. 


199 

Leaflets of compound leaf . . 

277 

Linden tree. 

364, 

352 

Lean meat, example of protein 

416 

Linen, furnished by flax family 

299 

Leather. 

443 

source of clothing . . 


376 

indirect product of plants 

376 

use of bacteria in manufac- 


made from skins .... 

460 

turing. 


311 























































22 


INDEX 


References 


Lingual ribbon.190 

Linseed oil, source of . . . . 223 

Lions.137 

Lipoid.479 

Lips of frog.85 

Liquor license required 506 

List of subjects studied by 

Bureau of Entomology . 525 

Litmus, dye from lichen . . . 326 

Liver.409 

Liver flukes.176 

Liverworts.9, 331 

Lizards.99, 101 

horned toad, example of . 101 

Lobes, olfactory.88 

Lobster protected by law 520 

Location of nerves in man . 466 

Lockjaw.511 

Locomotion, of fish .... 72 

of starfish . . . . '. . . 171 

Locust, a tree.299 

Loment, a fruit.237 

Longitudinal muscles of earth¬ 
worm .179 

Louse, carrier of disease . . 514 

Lumber, from gymnosperms . 346 

from hardwood trees . . . 351 

furnished by walnut family . 297 

how cut.363 

Lumbering, compared with 

forestry.347 

operations, forests destroyed 

by.363 

Lungs, of frog.87 

of birds.109 

of man.444 

Luxuries, fleshy fruits . . 234 

of food from rose family . . 298 

Lymph. 454 

Lymphatic circulation .... 454 

Lymphatics.455 

M 

Mackerel, a bony fish ... 71 

Madreporic plate.170 

Maggots, larvae of flies ... 28 

Magnesium, a salt.412 

Magnesium sulphate in Pas¬ 
teur solution.322 

Mahogany, use of, as furniture 

veneer.352 


are to pages 


Malaria.493 

caused by mosquito . .55, 493 

protozoan disease . . 489, 493 

Malarial parasite .... 55, 493 
Mallow family, importance of 299 
Mammalia, classified .... 9 

discussed.125 

number of. 9 

report on.135 

summary of.139 

Man, as an animal.399 

example of-mammal ... 9 

Mandibles of grasshopper 23 

Mandrake, medicinal plant . 256 

Mantle of mollusk.185 

Maple sirup.351 

trees, products of ... 351 

Maple wood, use of ... 352 

Marchantia.330 

Marrow of bone.436 

Marsh hawk, partly harmful . 115 

Martins, mosquitoes eaten by . 56 

Massasauge, a rattlesnake . . 101 

Masts, use of gymnosperms for 346 
Material for clothing .... 376 

Matter, organic and inorganic . 10 

Maturity, a period of l ife . . 402 

May beetle, harmful insect. . 34 

May flies, member of order 

Ephemeridae.29 

Meadow lark, food of. . . . 117 

nest of.112 

Measles, probable cause of . . 489 

Measuring worms, caterpillars 28 
Meat 

indirect product of plants . 376 

lean, use of, as food . . . 416 

Mechanical tissues of pteris 

stem.334 

Median fins of fish ... 71, 72 

Medicinal members of crow¬ 
foot family, list of . . . 297 

Medicines furnished by crow¬ 
foot family.297 

Medulla, of frog.89 

of man.481 

Medullary layer of kidney . . 458 

Medullary rays, of pine . . . 342 

Medullary sheath of nerve . . 468 

Medusa, described.165 

hy droid.164 









































INDEX 


23 

References are to pages 


Menhaden, example of bony 

fish.71 

Mercury poison.487 

Meristem. 247, 267 

Mesentery of frog. 86 

Mesoglea of coelenterate . . 160 

Mesophyll of leaf.285 

Mesophytes, definition of . . 372 

Mesothorax of grasshopper . . 23 

Metal container dangerous for 

milk.316 

Metamorphosis ..26 

complete.27 

incomplete.26 

Metathorax of grasshopper . 23 

Metazoa, defined.152 

Method of pollination, basis of 

classification.210 

Methods, of breeding oats . . 389 

of attracting birds . . . . 117 

of control of house-fly ... 56 

Meyer, Hans, discovery of . . 480 

Mice, destroyed by hawks . . 115 

harmful mammals .... 135 

Microbes, a name for bacteria . 309 

Micropyle, of bean.219 

use of.220 

Microscope, inventor of . . . 316 

Middle ear.475 

Middle West, production of 

corn by. . 296 

Midrib of marchantia .... 331 

Migration of birds.113 

Milk, care of.316 

curd of, example of protein . 416 

from healthy cow, number of 

bacteria in.313 

indirect product of plants . 376 

Milk glands, characteristic of 

mammals.125 

Milt of fish.78 

Mineral matter in food ... 15 

Mineral substances .... 15 

Mink, harmful mammal . . . 137 

Mint family, characteristics of . 300 

Mints used for medicine and 

in food.-300 

Mistletoe, absorbing organs of 369 

a semi-parasite.369 

Mites, arachnids.65 

Mixed diet of man.411 


Model reservoir.463 

Modifications of plants . . . 366 

Modified cotyledon (scutellum) 

of corn.225 

Modified leaves of club moss . 338 

Moisture, a condition for 

growth of bacteria . . . 310 

for lichen gathered by fungus 325 

Molars of man.406 

Molds, classified. 9 

Moles destroyed by hawks . . 115 

Mollusca, classified .... 9 

number of. 9 

Mollusks, characteristics of . 185 

life history of.188 

shells of, home of hermit crab 65 

summary of.67 

Molting, of crayfish .... 61 

of grasshopper.25 

Monarch butterfly .... 39, 41 

Monkey, example of mammal . 9 

Monocotyledons, group of 

flowering plants .... 9 

represented by corn . . . 226 

seeds of. 227 

Monoecious flower, defined . 204 

of beech family.297 

of walnut family .... 297 

Morning glory, an annual plant 261 

a dicotyledon.227 

Mosquitoes, breeding places 54, 494 
members of Diptera ... 54 

Moss, composition of cushion of 328 
two generations of ... 330 

Mosses, and their allies . . . 328 

classified. 9 

general features.328 

habitat.328 

life history of.328 

number of. 9 

Moths, carriers of pollen ... 41 

example of Lepidoptera . . 39 

Moths and butterflies, field 

study of.44 

Motile cells (sperms) of moss 

plants.329 

Motion, a fundamental function 4 
Motor function of nerves . . 470 

Mouth, cavity of earthworm 181 

of man.404 

Movable joints.435 



































24 


INDEX 


References 


Movements, of leaves . . . 290 

of plants.369 

Mucous glands of fish ... 72 

Mucus, use of, by clam . . . 188 

Mule.129 

Mullein, flowers of.217 

Multiple fruits.240 

Muscle, bundle.437 

Muscle cells, heart .... 437 

fibers.437 

involuntary.437 

voluntary.437 

Muscles, color of.436 

involuntary.437 

of man, discussed . . 432, 436 

scars of clam.186 

voluntary.437 

Mushrooms, edible fungi 324 

poisonous.324 

Mustard, a common plant fam¬ 
ily . 222, 298 

Muzzling of dogs.509 

My a arenaria, edible clam . . 193 

Myosin.14 

Myriapods, discussed .... 66 

N 

Nails, origin of.459 

Narcotic, defined.479 

Narcotics, use of.506 

Nasal cavity of fish .... 75 

Nasturtium flower, example of 

adaptations.196 

National forest preserves . 361 

Natural enemies of potato 

beetle.36 

Natural gas, formation of . . 340 

Natural immunity.510 

Natural rate of breathing . . 446 

Nectar, relation to pollination 

by butterfly . . . . 39, 40 

sought by insects . . 199, 208 

Needle-like leaves of pine . 343 

Need for a study of forestry 347 
Nephridia of earthworm . . . 180 

Nereis, an annelid worm 184 

Nerve cells.466 

of mollusks.188 

Nerve fibers, defined . . 466 

description of.466 


are to pages 


Nerve fibers — Continued 

gray substance of ... 468 

white substance of . . . . 468 

work of.470 

Nerve pathways in midbrain 89 
Nerve supply of muscles . . . 438 

Nerves, cranial, of frog ... 89 

location of.89 

of earthworm.181 

of frog.89 

of mollusks.188 

Nervous system, growth of . . 468 


in grasshopper.25 


of crayfish.64 

of earthworm.181 

of frog.88 

of man.466 

parts of.466 

summary of.485 

Nest-building of birds . 112 

Nesting boxes.119 

Net-veined leaf.276 

New discoveries, discussed . . 521 

New ideas, value of ... 526 

Nighthawks, destroyers of mos¬ 
quitoes .56 

food of.115 

Nightshade family, character¬ 
istics of.300 

Nissl bodies.481 

Nitric acid, test for protein . . 228 

Nitrogen, a chemical element . 13 

gathered by bacteria . 256, 311 

in lipoid.480 

proportion of, in living things 13 

Node of corn stem.268 

Non-motile cells (eggs) of moss 

plants.329 

Non-smokers, scholarship of . 485 

Normalbodytemperatureof man 459 

Norway maple.364 

Nose, sense organ.472 

Notochord, embryonic structure 

of fishes.68 

Nourishment, defined .... 415 

Nucellus.219 

Nuclei of pollen and egg . . . 212 

Nucleoli of cells. 7 

Nucleus, of cell. 7 

of nerve cell, action of alcohol 
upon.481 









































INDEX 


25 


References are to pages 


Nucleus — Continued 

of pleurococcus.304 

Nurses, care of bee larvae by . 46 

Nuthatches, at suet station . . 118 

destroyers of Lepidoptera . 42 

useful birds.114 

Nutrients, defined.13 

Nutrition a fundamental func¬ 
tion . 5 

Nuts, from hardwood trees . . 351 

furnished by walnut family . 297 

indehiscent fruits .... 237 

Nymphs of cicada.33 

O 

Oak leaf.297 

trees. 352, 364 

Oat plant, root system of . . 252 

Oats, a cereal .... 244, 295 

a monocotyledon .... 227 

member of grass family . . 295 

types of heads of .... 389 

Obesity cures.504 

Obnoxious plants, names of 301 
Octopus, example of mollusk 185, 191 
Odonata, order of insects . . 29 

Odor, use of, in flowers . 199 

Odors of other foods absorbed 

by milk.316 

produced by fermentation . 211 

Oils, tests for.228 

Oils, a class of foods .... 416 

Old age, a period in life history 402 
Olfactory lobes, function of . • 89 

of frog ..88 

One-celled plants.364 

Onions, storage of food in . 379 

Operculum of fish.71 

Opium, a poison . . . 487, 506 

Optic lobes of frog.88 

Optic nerve.474 

Oral side of starfish . . . 170 

Orange, exapaple of berry . 233 

Orbits, defined.472 

Orchard fruits from rose family 298 
Orchids, greenhouse epiphytes . 373 

roots of.253 

Organ, defined. 6 

part of body. 7 

system. 7 


Organic foods.410 

matter, example of ... . 10 

Organism, beginning of new . 6 

study of. 8 

sensation in. 6 

Organs, defined. 7 

of circulation of fish ... 75 

of crayfish.63, 64 

of earthworm .... 180-182 

of frog.85-89 

of plants.195 

of respiration in man . . . 444 

Organ system, defined ... 7 

part of body. 7 

Orioles, food of.42 

nest of.112 

Orthoptera, order of insects . . 29 

Osmosis, defined.15 

in absorption of food . . 414 

in photosynthesis .... 282 

in root hairs.248 

in sponges.156 

Outer coat of pollen grain 208 

Outer ear.475 

Outer skeleton, of crayfish . . 61 

of turtle.100 

Ovary, of ccelenterates . 165 

of frog.87 

part of pistil.198 

Overeating, results of ... 504 

Overwork predisposes to tu¬ 
berculosis .497 

Oviducts of frog.87 

Ovipositor of grasshopper . . 24 

Ovules, change to seed in . . 219 

described.212 

of pine.344 

Owl, feet and beak of. . 108, 109 

screech, beneficial . . . . 115 

snowy, a winter visitant . . 112 

Oxalis .291 

Oxen.132 

Oxidation, defined.12 

in birds.109 

Oxygen, a chemical element 12 

a condition for the growth-of 

bacteria.310 

proportion of, in living things 13 
test for ....... 281 

use in respiration .... 5 

use of, by birds.HO 


































26 


INDEX 


References are to pages 


Oysters, artificial raising of . . 193 

destroyed by starfish . 173, 193 

examples of mollusks . . . 185 

study of, by Bureau of Fish¬ 
eries .526 

P 

Palate of man.406 

Palisade cells of leaf .... 285 

Palmately compound leaves 277 

Palps of clam.188 

Panama Canal, a health prob¬ 
lem .494 

Pancreas of man.409 

Pancreatic juice, enzymes in 412 
Paper, made from wood pulp of 

spruce trees.346 

Papilionaceous flowers . . . 299 

Papillae of tongue.404 

Pappus, use of ... . 239, 241 

Paraffin, in transpiration ex¬ 
periment .284 

Parallel venation.276 

of leaves of lily family . . . 297 

of grass leaves.295 

Paramecium ..146 

example of protozoa . . . 149 

mode of defense.147 

study of.146 

Parasites, action of .... 

176-178, 320, 488, 493 

group of fungi.320 

ichneumones.41 

liver fluke.175, 176 

plants, modifications of . . 366 

tapeworms.495 

Thalessa.51 

Parasitic fig wasp.243 

. Parasitism, a dependent rela¬ 
tion .57 

Parsley family, characteristics 

of.300 

list of plants in.300 

Parsnips, member of parsley 

family.300 

storage of food in ... 252 

Partridge, wings of .... 108 

Parts of a flower found in nas¬ 
turtium .198 

Parts of a leaf.276 


Parts of a lily.200 

Parts of nervous system in 

man.466 

Passer domesticus, scientific 

name of English sparrow . 10 

Pasteur, discoverer of lactic 

acid bacteria.316 

study of bacteria by . . . 316 

Pasteurization, defined . . . 314 

Pasteurized milk.314 

Pasteur solution, formula of 322 
Patent medicines, defined 501, 506 
to be avoided in consumption 492 
Patrolling of forests .... 360 

Peaches, produced by rose 

family.298 

Peach-tree borer.39 

Peanut, peculiar habit of . 299 

Pea plant, modified leaves of . 290 

member of bean family . . 299 

Peanut shucks as adulterant 428 
Pears, example of pome . . 234 

Peat.340 

Pectoral girdle of vertebrates . 69 

Peculiarities of plant life . . 366 

Peculiar uses of leaves . . . 289 

Pedal ganglion of clam . . . 188 

Peg of hypocotyl.220 

Pelvic girdle of vertebrates . . 70 

Pelvis, of kidney . . . . . 458 

of trunk of man.458 

Penguins, use of wings . . . 107 

Pennyroyal, a medicine . . . 300 

Peony. 252, 297 

Pepo.237 

Peppermint.300 

Pepsin, an enzyme.14 

Peptone in agar-agar formula 312 

Perch, a bony fish.71 

classified. 9 

Perennial roots.252 

Perfect flower, definition of 199 
Perianth of lily family . . . 297 

Periblem.247 

Pericardium, of clam .... 187 

of man. 452 

Pericarp.233 

Permanent residents . . . ill 

Permanent teeth.407 

Perspiration, discussed . . . 459 

Petals, described.198 

























INDEX 


27 


References are to pages 


Petiole, of leaf. 


276 

Pitcher plant. 


289 

of clematis. 


289 

use of leaves in ... . 


366 

of nasturtium .... 


.288 

Pith in corn stem . . . . 


267 

Petroleum, formation of . 


340 

Placenta of flower . 


200 

Petunias, members of night- 


Plague of locusts 


30 

shade family .... 


301 

Plague, an epidemic disease 


514 

Phanerogams, a group of plants 

8 

Planarian worm 


175 

Pharynx, of earthworm . 


181 

Plantain, a weed . 


239 

of man. 


406 

Plant, biology. 


195 

Pheasant, a seed eater 


117 

breeding. 


388 

wings of. 


108 

conditions, change of . 


266 

Phlegmatic temperament, heart 


diseases . 


380 

tracing of. 


483 

ecology, defined . . . . 


374 

Phloem, discussed .... 


266 

food, of interest to farmer 


273 

conducting food materials 


269 

lice. 


32 

position in woody stem 


267 

members of Hemiptera . 


32 

position of, in vascular bundle 

266 

protected by ants 


53 

Phoebes, destroyers of Lepidop- 


life, mystery of ... 


378 

tera ....... 


43 

peculiarities of . . . 


366 

Phosphates. 


416 

or animal matter food 

of 


Phosphorus, a chemical element 


bacteria. 


310 

found in living things . 

13, 412 

Plant societies. 


369 

a poison. 


487 

Plant succession .... 


374 

in lipoid. 


480 

Plants as organisms, interest in 

378 

useful in body .... 


416 

Plasma. 


449 

Photosynthesis, defined . . 


278 

Plecoptera, order of insects . 


29 

finished product of . 


279 

Plerome of stem .... 


.247 

importance of .... 


279 

Pleurococcus, described . 


304 

oxygen produced by . 


279 

Plum, example of drupe . 


239 

performed by stem . . . 


371 

produced by rose family . 


298 

use made of products of . 


279 

Plumage, discussed . . . 


110 

vital process in plants . 

274, 

278 

Plumes on wind-distributed 


Phototropism. 


286 

seeds . 


241 

Phylloxera, injurious insect . 


531 

Plumule, connection with seed 


Physical change described . 


16 

leaves. 


221 

Physical training, value of . 


440 

defined. 


221 

Pieplant, storage of food in . 


252 

part of embryo .... 


221 

Pigment in skin .... 


459 

Pneumonia. 

449, 

489 

Pigs, important mammals . 


133 

Pod, form of fruit .... 


237 

Pike, a bony fish .... 


71 

Poison, defined. 


487 

raised in hatcheries . 


78 

in tobacco smoke 


485 

Pimples. 


504 

Poisonous character of crow- 


Pine, discussed . . . • 9, 

341- 

-344 

foot family. 


297 

tree, described .... 


341 

of lizards, Gila monster . 


101 

yellow, lumber of 


352 

of plants of nightshade family 

300 

Pinnately compound leaves 

of 


of snakes. 


101 

walnut family .... 


277 

of toxins. 


311 

Pistil, described. 


198 

Pollen, cell necessary for pro- 


Pistillate flower, described . 


204 

ducing seed . . . 

202, 209 

of monoecious plant . . 


204 

distributed by wind . . 


210 

Pitch, source of. 


346 

of pine. 


344 






























28 


INDEX 


References are to pages 


produced by stamens . . . 

202 

Preparation of foods, discussed 

426 

sacs of pine. 

343 

of soil. 


231 

tube, formation of ... . 

201 

Preservation of wood . 


353 

of pine. 

210 

Preservatives, list of . 


314 

Pollen grains, growth through 


use of, in milk . . 


314 

pistil ........ 

2 ; 12 

Preventable diseases . 


497 

Pollination, by wind .... 

210 

Prevention of communicable 


definition of. 

208 

diseases . . . 


497 

step in production of fruit . 

209 

of epidemics . 


515 

Pollution of water . . . 462, 508 

Preventive measures against 


Polytricum, laboratory study of 

330 

sickness. 


517 

Pome, a fleshy fruit .... 

237 

Primary root. 


250 

Pond scum, habitat of 

305 

Problem of sewage disposal 

443 

Pond snail, discussed .... 

190 

Proboscis of butterfly . . 


39 

Poplars, as shade trees . 

364 

Products of cotton seeds 


222 

rapid growth of. 

352 

of photosynthesis 

• • 

279 

Poppy, capsule of . . . 238, 241 

Propolis, use of, by bees . 

, . 

49 

Pores of sponge. 

156 

Properties of wood 


354 

Porifera, classified. 

8 

Prop roots of corn . 


253 

Pork, inspection of . . 177, 500 

Protection of forests . 


357 

trichinella in. 

176 

Protective coloration, of birds . 

110 

Portal vein. 

414 

of grasshoppers . . . 


21 

Position of stems. 

260 

Proteid substances in 

flour 


Potassium, a chemical element 


source of food for 

yeast 


found in all living things 

13 

plant. 

427 

contained in food .... 

413 

Protein, a class of foods 

13, 415, 416 

Potassium permanganate, a dis¬ 


in bean . 


228 

infectant . 

512 

product of photosynthesis 

279 

Potassium phosphate in Pas¬ 


stored by bean . 


222 

teur solution. 

322 

Proteins of serum . 


428 

Potato, a food plant of the 


Prothallium of fern 


336 

nightshade family . . . 

301 

Prothorax of grasshopper 


23 

beetle, injurious insect . 34, 35 

Protonema, of fern 


336 

wart, a disease. 

380 

of moss. 


329 

discussed. 

382 

Protoplasm, of cell . . . 


7 

Poultry destroyed by certain 


of pollen grain 


209 

hawks. 

115 

Protozoa, cause of disease 


489 

Powdery mildew. 

531 

classified . ... 


8 

Power of health officials . . . 

519 

flagellate. 


149 

Practical problems connected 


number of kinds of . . 


8 

with respiration and ex¬ 


resemblance to bacteria 


309 

cretion . 

443 

simplest animals . . . 


141 

Praecocial birds, defined . 

113 

Protozoa and alcohol . . 


150 

Prairie dogs, harmful mammals 

134 

Protozoan cell, described 


141 

Prairie horned larks at seed 


Protozoan diseases . . 


494 

station. 

118 

Pseudopodium of amoeba 


143 

Prairies suited to raising of corn 

296 

Ptarmigan, protectively colored 

121 

Praying mantids, a family of 


Pteridophytes, classified . 


9 

Orthoptera. 

29 

Pteris, described 

261, 

333 

Predigested foods, use of . . 

430 

Ptyalin, an enzyme 

411 


















INDEX 


References 

Public baths. . 517 

institutions, examination of 

servants for.501 

Public markets.426 

museums.122 

parks.517 

preserves.. 124 

Puffball, example of fungi . . 9 

spores of, “ smoke ” ... 328 

Puffins, nest of.112 

Pulmonary tuberculosis, dis¬ 
cussed .489 

Pulse caused by beating of 

heart.454 

Pulse, members of bean family 299 

Pulse family.376 

discussed.299 

foods furnished by . . 222, 228 

list of plants of.299 

value to the soil of plants of . 256 

Pulvinus.291 

Pupa, stage in the metamor¬ 
phosis of insects .... 27 

description of.27 

Pupil of eye.473 

Pure culture, defined .... 316 

of nitrogen-gathering bac¬ 
teria .259 

of yeast plant.321 

Pure food laws.428 

Pure milk, cost of producing . 314 

Purpose of respiration 446 

Purslane, a weed.239 

Pustules on wheat stems 385, 386 
Pyloric valve of stomach . . . 408 

Python, a constrictor .... 102 

Q 

Quack, defined.501 

Quack grass.261 

Quail, a seed eater . . . 117 

food of.35, 36 

Qualifications of a forester . . 361 

Quality of work a test 477 

Quarantine against insects . 522 

defined.308 

laws.509 

regulations.508 

violation of.508 

Quarter-sawn timber .... 354 

Queen bee.46 


29 

are to pages 

R 


Rabbits, destroyed by hawks . 115 

harmful animals.134 

Raceme.214 

Radial arrangement of starfish 169 
Radish, a dicotyledon . . . 227 

member of mustard family . 298 

storage of food in roots of . 253 

Range of plant’s territory, how 

increased.240 

Rank-scented foliage of night¬ 
shade family.301 

Raphe of beans.227 

Raptores, discussed . . . . Ill 

Raspberry, in plant succession . 375 

example of aggregate fruit . 239 

produced by rose family . . 298 

Rats, destroyed by hawks . 115 

harmful animals.135 

Rattlesnake, a poisonous snake 101 

fangs of.101 

poison, effect of.488 

Raw materials of photosynthesis 279 
Raw milk, danger from . . . 315 

Ray flowers of composites 206 

Rays of starfish.169 

Receptacle, part of flowers 201, 233 
Reclamation of land .... 391 

by draining.392 

Reclamation projects .... 392 

Rectum, part of digestive 

system. 404, 409 

Recovery from fatigue of 

muscles.439 

Redbud, member of pulse 

family.299 

Red corpuscles of blood . . . 449 

Red rust of wheat, a fungus 324 
Red-shouldered hawk . 115 

Red squirrels, harmful animals 135 
Redwood trees, age of . . . 261 

Reflex action, discussed . . . 469 

in the earthworm .... 471 

in the frog.471 

in the hydra.471 

Reforestation.356 

Refrigeration of foods . . . 497 

Regeneration, defined . . 174 

Regular flowers, defined . . • 204 

of mustard family .... 298 



































30 


INDEX 


References are to pages 


Reindeer, food of.326 

useful animal.134 

Rejuvenation of worn-out land 394 
Relapsing fever, epidemic dis¬ 
ease .514 

Related forms of conifers 345 

Relation of heredity to human 

progress.535 

Relation of sponge to other 

animals.158 

Relation of vaccination to hu¬ 
man progress ..... 510 

Relationships of plants an in¬ 
teresting study . . . . 378 

Remedies, plants a source of . 376 

Reproduction, a life process . . 5 

asexual, defined.157 

of amoeba . 145 

of bacteria.310 

of fishes.77 

of grasshopper.25 

of hydra.163 

of paramecium.148 

of yeast plant.322 

simplest form of.305 

Reproductive bodies of pteris 334 

Reproductive glands of starfish 170 
Reproductive hyphae of bread 

mold.323 

Reptiles, discussed.99 

life history of.99 

summary of.106 

Reptilia, classified. 9 

number of. 9 

Residents, birds classed as . . Ill 

Resin, source of.346 

Resistance to disease .... 530 

Respiration, a fundamental 

function. 5 

a two-fold process . . : . 146 

described.. 5 

artificial, described .... 448 

in man.443 

organs of ...... 444 

of amoeba.145 

of plants.229 

of grasshopper.21 

of hydra.163 

of mollusk.188 

of paramecium.148 

of starfish.172 


Respiration — Continued 

produces carbonic acid gas 5, 446 


purpose of.5, 446 

student report on ... 444 

Respiration and excretion . . 443 

Rest, effect cf, in consump¬ 
tion . 491 

necessity for, in keeping well 440 

relieves fatigue.440 

Resting stage (pupa) of codling 

moth.27 

Restricted diet of primitive life . 410 

Retina.474 

Review and summary, of assimi¬ 
lation .541 

of cellular structure of organ¬ 
isms .538 

of circulation.541 

of community life .... 544 

of conservation.546 

of Department of Agricul¬ 
ture and Forestry . . . 548 

of digestion.540 

of excretion.542 

of food-getting of animals . . 540 

in plants.540 

of interdependence of animals 

and plants.543 

of living tilings.538 

of natural and artificial selec¬ 
tion .549 

of plant and animal improve¬ 
ment .548 

of principal functions . . . 539 

of protoplasm.538 

of public health ..... 547 

of relation of plants and ani¬ 
mals to man.544 

of reproduction.542 

of respiration.541 

of sensation.542 

Rhizoids, of marchantia . . . 331 

of mosses.328 

Rhubarb, medicinal plant . . 255 

Ribbed stem of parsley family . 300 

Rib of leaf.276 

Rice, amount produced in U. S. 296 

a cereal..244 

member of grass family . . 295 

use of, in China and India . 296 

Rind of corn stem.268 














































INDEX 


31 


References 


Ripened ovary, the fruit of a 

plant.233 

Roadsters or trotting horses 129 

Robber bees.47 

Robin, a useful bird . . . 114 

food of.115 

sometimes a permanent resi¬ 
dent .113 

Rochelle salts in Fehling’s solu¬ 
tion .228 

Rock oil, formation of 340 

Rocks, habitat of lichens . . 325 

habitat of pleurococcus . . 304 

Rod-shaped bacteria .... 309 

Root, the.247 

Rootcap.247 

Root hairs, discussed .... 248 

Roots, of alfalfa.252 

of beet.255 

of pine.343 

Root system of alfalfa . . . 252 

of wheat plant.252 

Rose, a common plant family . 298 

leaves of.298 

family, discussed .... 298 

foods furnished by . . . . 376 

Rose-breasted grosbeak, de¬ 
stroyer of potato beetles . 36 

Rosette formation of leaves 289 
Rosette of moss plant 329 

Rotating crops, reason for 257, 394 

Rough lumber.363 

Round clams.192 

Round leaves of sundew . . 367 

Rudimentary toes of cow . . 126 

Rules of hygiene.317 

Runners (stolons).271 

Rushes related to ferns . . 333 

Russian thistle.242 

Rye, a cereal.244 

a monocotyledon .... 227 

member of grass family . . 295 

S 

Saddle horses . 129 

Saffron, flowers of . 217 

Sage, a member of the mint 

family.300 

Sailing birds, examples of . . 108 

wings of . 108 


are to pages 


Salamander, classified ... 9 

discussed.82 

Saliva, use of, in man .... 411 

of mosquito.494 

Salivary glands, of man, loca¬ 
tion of.409 

of mosquito.494 

Salmon, example of bony fish . 71 

in hatcheries.78 

Salt, a fundamental taste . . 405 

common, scientific name of . 412 

use of, in preserving meat . 313 

Salt-rising bread.427 

Salts in food.15 

Samara.237 

Sand swallow, nest of ... 112 

Sand worm.184 

Sanitary measures.498 

nuisances.519 

officers.519 

Sanitation, effect of in prevent¬ 
ing disease.497 

San Jose scale, an injurious 

insect.34 

Sap, compared with blood . 269 

conducted by vascular 

bundles.281 

Saprophytes, group of fungi 321 

Sapwood.353 

Sardines, example of bony fish . 71 

Savory, member of mint family 300 
Sawdust, adulterant .... 428 

Scale insects, spray for ... 32 

Scale-like leaves of cedar 345 

Scales, of fish.72 

modifications of skin . . . 459 

Scales of staminate cone of pine 343 
Scallops, edible mollusks . 193 

Scarlet fever, probable cause of 489 
Scars, characteristic of stem . 264 

Scholarship, effect of smoking 

tobacco, on.485 

Scientific interest in plants . 377 

Scion.271 

Sclerotic coat of eye .... 473 

Scorpions, example of Araeh- 

nida.65 

Scouring rush.339 

Screech owl, a useful bird . . 115 

Scrub stock improved by graft¬ 
ing .271 










































32 


INDEX 


References are to pages 


Scutejlum, digestive organ 

of 


Selective cutting of forests . . 

362 

corn grain . . . 4 


225 

Self-pollination, discussed . . 

211 

modified cotyledon . . 


225 

preyention of. 

211 

Scutes of snake.... 


101 

Self-protection of earthworms . 

183 

Sea-anemone, described . 


166 

Semi-circular canals of ear . . 

475 

member of ccelenterates 

160 

166 

Sensation, a life process . . . 

5 

Sea-cucumber, member 

of 


Sense organs, list of ... 

472 

echinoderms . . . 


169 

of touch, location of . . 

472 

Sea-fans, described . . 

160, 167 

Senses, use of, in grasshopper . 

25 

member of coelenterates 


160 

Sensitive plants. 

291 

Sea-lily, member of echinoderms 

169 

Sensory function of afferent 


Sealing, object of . . . 


313 

nerves . 

471 

Seals. 


526 

Sepals, described ..... 

198 

Sea-plumes, described . 


167 

Sepia, described. 

192 

Sea-turtle. 


100 

Serrate edge of leaf .... 

278 

Sea-urchins, classified . 


8 

! Serum. 

511 

members of echinoderms . 


8 

Seta of moss sporophyte . 

330 

Sea-weed, removal of, from 


Setae of earthworm .... 

179 

oyster beds. 


173 

Setting of bones. 

435 

Sea-worm a true worm . . 


175 

Setting-up exercises .... 

440 

Secretions of sundew, use of 

367 

Seventeen year locust (cicada) 

33 

Seed, development of . 


219 

Severe cold, effect of, on 


distribution of ... 


240 

plants. 

373 

of pine. 


344 

Sewage, improper care of 

461 

of strawberry. 


240 

Sexual reproduction . . 157, 307 

Seed-bearing plants, a group 


of hydra. 

163 

of plants. 


9 

of spirogyra. 

305 

Seed bud (plumule) . . . 


221 1 

Sexual spore. 

307 

Seed coat (testa) . . 

219, 

220 

Shad, example of bony fish . 

71 

“ Seed ” corn. 


245 

raised in hatcheries .... 

78 

Seed dispersal. 


240 

Shade trees. 

364 

Seed-eating birds . . 


116 

Shaft of bone. 

436 

bills of. 

109, 

116 

Shaggy cap or cover of moss 


claws of. 


108 1 

capsule . 

328 

Seedless plants, a group 

of 


Shape and size of bacteria . . 

309 

plants. 


9 

Sharks, a division of fishes . 

79 

Seedling, defined . . , . 


221 

Sharp-shinned hawk, partly 


Seed-producing organs of pine . 

343 

harmful. 

115 

Seed selection. 


231 

Sheep . 

132 

Seed wheat. 


245 

example of mammal 

9 

Seeds, of berries 


241 

Shell of slug .... 

185 

devices for distributing 

238, 242 

of snail. 

190 

food of birds. 


116 

Shepherd’s purse, a weed . . 

223 

improvement in, by cross- 


Shrews destroyed by hawks 

115 

pollination. 


390 

Shrike (great northern), a win¬ 


of cotton. 


222 

ter visitant. 

112 

of weeds. 


223 

Shrimps. 

526 

Segments. 


175 

Sickness, student report on 

487 

Selaginella, member of fern 


Sieve plates .... 

267 

group. 


337 

Sieve vessels of phloem . . . 

267 

Selection. 


390 

use of. 

269 






































INDEX 


33 


References are to pages 


Silica in corn stem.268 

in skeleton of sponge . . . 158 

Silique of mustard family (fruit) 298 
Silk of corn, attachment of 204, 225 

the style.198 

Silver maple, poor shade tree . 364 

Simple leaf, of beech family . 297 

defined.277 

Simplest green plants .... 304 

Sinus, defined.64 

Siphonaptera, an order of in¬ 
sects .29 

Siphons of clams.185 

Siphons of soft-shelled clam 191 

Sirup, maple .351 

Skate, edible fish.79 

Skeletal structures, student re¬ 
port on.436 

Skeleton, external, of corals 167 

of crayfish.60, 61 

of man.433 

characteristics of . . . . 434 

summary of.441 

of protozoa.149 

Skin, as sense organ .... 458 

described.458 

example of organ .... 7 

of fruit.243 

Skunk, example of harmful 

mammal.137 

Sleep, amount needed . . . 476 

Sleep movements of plants 291 

Sleeping sickness, how spread . 494 

probable cause of ... 489 

Slimy feeling of spirogyra . 307 

Slimy substances of sponge re¬ 
moved by bacteria . . 311 

Slips producing adventitious 

roots.254 

Slug (garden).190 

Slugs, examples of mollusks 185 
Small cells, position of, in an¬ 
nual ring.266 

Smallest plants.309 

Small intestine, of frog ... 86 

of man.408 

Smallpox, Jenner and .... 510 

lessened by vaccination . • 510 

probable cause of . • • 489 

Smell, organ of, in grasshopper 21 
sense of.472 


Smilax. 263, 290 

Smoke, result of chemical 

change.10 

of puffball.328 

Smoker’s heart; effect of to¬ 
bacco illustrated .... 482 

Smoking and scholarship . . 485 

Smoking of meat, purpose of 313 

Snails, discussed.189 

examples of mollusks . 9, 185 

respiration in.190 

tongue of.190 

Snakes (black), harmful . . . 102 

discussed.101 

examples of Reptilia . . 9, 99 

fear of.102 

food of.101 

Snowy owl, a winter visitant . 112 

Soap in cosmetics.504 

Soda, a nutrient, use of . . . 416 

preservative.314 

Sodium carbonate in artificial 

pancreatic juice .... 413 

Sodium chloride, scientific name 

for common salt .... 412 

Soft palate of man.406 

Soft-shelled clam, an edible 

mollusk.193 

discussed.193 

Soil, an element of success in 

agriculture.376 

upper layers, habitat of bac¬ 
teria .310 

Soil bacteria.256 

Soldiers, a class of ants ... 52 

Soles of feet, animals that walk 

on. 126 

Solitary flower.213 

Some general plant problems . 380 

Song sparrow, at hemp and 

millet station.118 

killed by hawks.115 

useful bird.H4 

Sorghum.421 

Sori, of ferns.334 

Sounds from sound waves . 475 

Sour, a fundamental taste . . 405 

Sour bread, cause of ... . 427 

Source of malarial parasite . 493 

Source of man’s food supply . 419 

Sources of danger in milk • 315 






























34 


INDEX 


References are to pages 


Souring of milk, cause of . . 314 

Southern cattle tick . . . 460 

Spanish influenza.493 

Sparrow, chipping, useful bird 114 

example of bird. 9 

fox, example of transient bird 112 
hawk, destroyer of grass¬ 
hoppers .31 

destroyer of cicadas ... 34 

Sparrows, seed-eaters .... 117 

Spawn, migrations of fishes to . 76 

Spearmint, member of mint 

family.300 

Special modifications of plants 

356-372 

Special senses, organs of 75 

Specialized roots.252 

Specialized stems.263 

Speed a test of efficiency . . 477 

Sperm, cells of fishes .... 78 

cells of fern.336 

.nucleus of pollen grains . . 209 

of moss plant.329 

of volvox.153 

Spermaries of hydroids . . . 165 

Spermary of frog.87 

Sphinx moth from tomato 

worm 40 

Spicules, described .... 156 

Spider, member of Arachnida . 65 

Spinal column of man, curves of 434 
Spinal cord, part of nervous 

system.89 

Spines of echinoderms 169 

Spiracles, of grasshopper 22 

Spiral arrangement of scales on 

cones.343 

Spiral bands of chlorophyll in 

spirogyra.306 

Spirillum, a form of bacterium . 309 

Spirogyra, example of algae . . 304 

described.305 

reproduction of.306 

Spirogyra and pleurococcus, 

summary of.308 

Spleen of frog.87 ! 

Splints, use of in setting bones . 435 | 

Spoiling of food by bacteria 313 
Sponges, classified .... 8 

described.155 

discussed. 155-158 


Sponges — Continued 

economic importance of . . 157 

example of Porifera ... 8 

how gathered.158 

how prepared.158 

relation to other animals . . 158 

structure of.155 

summary of.158 

use of bacteria in preparation 

of.311 

where obtained.158 

Spongilla, reproduction of . 157 

Spongy layer of leaf .... 285 

tissue of velamens .... 373 

Sporangia, of ferns.334 

Spores, of bread mold . . . 325 

of club moss^ ..339 

of moss.328 

Sporophyte, dependence of . . 330 

generation of moss .... 330 

Sprain, defined.435 

Spraying to destroy insects . 43 

Spread of biological diseases 537 
Springs, source of water supply 463 
Spruce, a gymnosperm . . . 345 

example of gymnosperm . . 9 

Spur, part of flower .... 202 

Sputum, destruction of, neces¬ 
sary .490 

spread of tuberculosis by . 490 

Square stems of mint family . 300 

Squash, a dicotyledon . . . 227 

a fruit.245 

Squid, described.191 

example of cephalopods . . 191 

of mollusk.185 

Squirrels, damage done by . 135 

hinder reforestation . . . 357 

Stamens, described .... 198 

Staminate cones of pine . . . 343 

Staminate flower.203 

of monoecious plants . . . 204 

of willow.204 

Staminate strobili.343 

Starch, a nutrient.13 

chemical composition of . . 13 

form of carbohydrate . . . 416 

in cosmetics.504 

in flour.426 

Starfish, classified. 8 

described.169 































INDEX 


References 


Starfish — Continued 

enemy of oyster.173 

family.169 

summary of.174 

State Department of Health 508 
Statistics of life insurance com¬ 
panies .478 

Steam, a form of water ... 10 

Steapsin, a ferment .... 412 

Steering, use of fins for ... 72 

Stegomyia, a mosquito ... 55 

Stem, of conifer.341 

of corn.267 

of ferns.334 

of mosses. . 328 

of xerophytes, green color of . 371 

Stems, discussed.260 

Sterile, defined.313 

Sterile hairs, of moss plants . 329 

Sternum, keeled, of birds . . 109 

Sticklebacks, nests of ... . 80 

Stigma, part of pistil .... 198 

feathery.210 

Stimuli, causing movement 290, 369 

list of. 6 

Stinging cells of ccelenterates . 160 

Sting of bee.46 

Stipules, of pulse family . . . 299 

part of leaf.276 

Stock.271 

Stolon.271 

Stomach, a digestive organ . . 86 

example of organ .... 7 

of man.408 

of starfish, use of, in food¬ 
taking .171 

valves of.408 

Stomach-intestine of earth¬ 
worm .181 

Stomata, number of ... 288 

in xerophytes.371 

of leaf.285 

position of, in waterlilies . . 287 

Stoneflies, members of Plecop- 

tera.29 

Stone fruits, defined .... 239 

Stone of drupe.239 

Stones, inorganic matter . 10 

wet by spray, habitat of 

mosses.328 

Storage of food in leaves 279, 293 


35 

are to pages 


Straight-veined leaves of beech 

family.297 

Stramonium, a medicine, source 

of.300 

Strap-shaped flowers .... 206 

Strawberry, description of . . 240 

produced by rose family . . 298 

Stream purification .... 462 

Street cleaning by flushing, 

advantage of.461 

String beans, value of, as food . 222 

“ Strings ” of celery .... 266 

Strobili, of pine.343 

staminate.343 

Structural changes due to 

alcohol.481 

Structure, of amoeba .... 143 

of bone.436 

of leaf.285 

of paramecium.146 

of pollen grain.208 

of roots.247 

of vascular bundle .... 266 

of woody stems.267 

Student report, on sickness . . 487 

on skeletal structures . . . 436 

on water supply.499 

Studies about plants, kinds of 

374-378 

Study of an apple.236 

Study of an orange .... 234 

Study of a tomato.235 

Study of lichens, field trip for 326 
Study of plants as organisms . 195 

Study of variation in wheat 529 
Style, part of pistil .... 198 

Substitutes for sugar .... 421 

Substitutes for butter .... 421 

Success in cultivating plants 376 
Suet, for winter feeding of birds 117 

station.118 

Suet-eating birds.118 

Suffocation, discussed .... 447 

Sugar, a nutrient.13 

broken up by yeast enzyme 

321, 427 

form of carbohydrate . . . 416 

in flour.• 427 

lessens fatigue.440 

obtained from maple trees . 351 

organic matter.10 




































36 


INDEX 


References are to pages 


Sugar — Continued 

product of photosynthesis . 279 

solution in study of spirogyra 307 

source of. 255, 376 

value of, as food. . . . 440 

Sulphur, a disinfectant . 512 

an element in animal and 
vegetable tissues .... 13 

sulphur dioxide.512 

Summary, of amphibians . . 98 

of arthropods.67 

of bacteria.317 

of birds. 124 

of circulation.465 

of conifers.365 

of digestion of man .... 431 

of disease.495 

of ferns and their allies . . 340 

of fish.81 

of flowering plants .... 302 

of fungi.326 

of hydra-like animals . . 167 

of mammals.139 

of mollusks.194 

of mosses and their allies . . 331 

of nervous system of man . 485 

of our interest in plants . . 397 

of protozoa.150 

of reptiles.106 

of simplest plants . . . . 317 

of skeleton of man . . . . 441 

of spirogyra and pleurococcus 308 

of sponges . - .158 

of starfish group.174 

of worm group.184 

Summer residents, examples of 112 

Sunburn.504 

Sundew, described . . . 289, 367 

rapid movements of . . 367 

sticky substance on leaves . 367 

use of leaves in.367 

Sunfish, care of eggs by . 80 

example of bony fish ... 71 

Sunflower, “ seed ” at feeding 

station for birds . . 117, 119 

Supply of oxygen kept up by 

plants.280 

Surplus food stored in roots 255 

Sutures of bone.434 

Swallows, destroyers of flying 

insects.115 


Swallow-tail butterfly, from 

celery worms.41 

larvae of.41 

Swampy land, reclamation of • 393 

Swarming of bees.48 

Sweat glands, discussed . . . 459 

Sweet, a fundamental taste . . 405 

Swifts, destroyers of flying in¬ 
sects .115 

Swimming pool (public bath) . 517 

Sycamore, useful shade tree . 364 

Symbiosis, defined.158 

example of, lichens .... 325 

nitrogen-gathering bacteria . 258 

Symptoms, medicines in con¬ 
nection with.501 

System (organ). 6 

T 

Tachina fly, beneficial insect . 54 

Tadpole, development of, from 

egg.91 

two stages in.92 

respiration of, by gills ... 92 

stage of frog.92 

Tail region of fish.72 

Talons, characteristic of birds 

of prey.Ill 

Tanning, use of hemlock bark 

in.346 

Tapeworm, a common . . 495 

classified.175 

Tap roots.250 

Tar, source of.346 

Tarsus of grasshopper’s foot 24 

Tartar, effect on gums . . . 407 

Tassel, staminate flower of corn 204 

Taste.472 

Technical names of parts of 

flower. 198-201 

Teeth, of adults.406 

irregular, of children . . . 407 

Telegraph poles, use of gymno- 

sperms for.346 

Temperament, nervous, effect 

of smoking on .... 483 

phlegmatic, effect of smoking 

on.483 

Temperate regions as a habitat 

of evergreens.344 








































INDEX 


37 


References 


Temperature, of birds . . . 110 

of fish.75 

of soil, an element of success 

in agriculture.223 

Tendon.438 

Tendrils, of pea plant . . . 290 

response of, to contact . . 369 

Tennyson, quotation from . . 379 

Tentacles of hydra.160 

Tent caterpillar.41 

Terminal bud.264 

cones in relation to . . . . . 345 

Ternately compound leaves . . 277 

Terrapin, use of, as food . . . 100 

Testa developed from integu¬ 
ment .219 

Testing seed.231 

Tests in bakeries and brew¬ 
eries .321 

Thalessa, larva of.51 

Thallophytes, classified ... 9 

Thallus of marchantia . . . 330 

Thickened fibrous roots . . 251 

Thick stems for food storage 261 
Thick-walled cells of annual 

ring, how formed .... 266 

Thigmotropism, discussed . . 286 

Thinning and transplanting 

seedlings.232 

Thin-walled cells, when formed 266 
Thistle, a common weed . . . 301 

Thoracic cavity.452 

Thoracic duct.414 

Thorax, of grasshopper ... 23 

Thorn, modified leaf .... 290 

Thorns.290 

Thousand-legged worms ... 66 

Thread-like hairs, of spirilla 

and bacilli.309 

Threads, of bread mold . . . 323 

of spirogyra.306 

Throat cavity of man .... 406 

of tadpole.92 

Thyme, a member of mint 

family.300 

Thyroid extract, use of . . . 504 

Thyrse.214 

Tibia, of grasshopper .... 24 

Tickle-grass.242 

Ticks, harmful insects ... 65 

members of Arachnida . . 66 


are to pages 


Tigers, harmful animals . . . 137 

Timbers of mines, use of gym- 

nosperms for.346 

Tissue. 7 

definition of. 7 

Tissues of fern.334 

Toad, horned.101 

Toadfish.79 

Toads, hibernation of . . . 84, 97 

Toadstools, example of fungi . 9 

Tobacco, effects of use of . . 482 

inhaling fumes.484 

member of nightshade family 300 
Tobacco worm, cocoons of 

parasite on.40 

Toes of cow, rudimentary . 126 

Tomato, a dicotyledon . . . 227 

food plant of nightshade 

family.301 

worms, larvae of sphinx moth 44 
Tongue, a sense organ . . . 404 

of man.404 

of snail.190 

Toothache, result of poor teeth 407 
Tortoise, use of, as food . . 100 

Toxin, bacterial poison . . 311 

of diphtheria.511 

secreted by bacteria . . . 311 

Trachea, of man.444 

of grasshopper.22 

Transient birds, examples of . 112 

Transpiration, defined . . . 282 

amount of water given off by . 284 

devices for retarding . 283, 371 

laboratory work on . . . . 284 

Trap-like device of Venus’s 

flytrap.367 

Tree sparrow, at bread crumb 

station.118 

Trees, habitat of lichens . . . 325 

Tremex borer, harmful insect . 51 

Trench fever.514 

Trichina, discussed . . . . 176 

Trichinella, discussed .... 176 

Trichinosis, cause of ... 177 

Trichocysts of paramecium . . 146 

Trillium, picking of .... 395 

Trochanter.24 

Tropical regions, first home of 

man.400 

home of epiphytes .... 373 
































38 


INDEX 


References are to pages 


Trout, example of fish 


9 

Umbrella-shaped branches of 


bony fish. 


71 

marchantia. 

331 

Trunk region of fish . . 


71 

Underground stems, described . 

261 

Trunks of evergreens . . 


341 

examples of. 

261 

Trypsin, an enzyme . . 


412 

of pteris. 

333 

Tsetse fly, sleeping sickness 


Undissolved food. 

415 

spread by ... . 


494 

Unhealthy cows, milk from . 

315 

Tube feet of starfish . . 


171 

Unicellular fungus, yeast an 


Tuberculin test, for cows 


315 

example. 

321 

discovered by Koch 


315 

United States Government De¬ 


Tuberculosis, a bacterial 

dis- 


partments . . . 500, 505, 

525 

ease. 


449 

Univalves. 

189 

discussed. 


489 

Unusual plants. 


in cows. 


315 

Unwashed hands, number of 


of throat and other organs . 

492 

bacteria on. 

312 

treatment for .... 


491 

Ureter, of frog. 

87 

Tubular appendages of male 


of man.. . 

458 

crayfish . 


64 

Urethra, of man. 

458 

Tubular flowers . . . 


206 

Urinary bladder of frog . 

87 

Tubules of kidney . 


458 

Uriniferous tubule. 

458 

Tulip tree. 


364 

Useful birds, examples of 114, 

115 

Tumors. 


488 

Uses, of fruits to man 

244 

Turgid cells. 



of parts of a flower .... 

202 

Turnip, example of biennial 


of stem, to man. 

261 

root. 


252 

to plant. 

261 

member of mustard family . 

298 

of terms “fruit,” “seeds,” 


storage of food in 


255 

etc. 

245 

Turpentine, source of . . 


346 

of wood. 

347 

Turtle, example of Reptilia 


100 



green, use of, as food . 


100 

V 


skeleton of .... 


100 



Turtles, discussed . . . 


100 1 

Vaccination, discussed . 507, 509 

Twining petiole, of clematis 

290 

Vaccine. 

510 

Twining stems .... 


260 j 

Vacuole, food, of amoeba . . 

144 

Two-parted flower of mint 


300 

contractile. 

145 

Tympanic cavity . . 


475 

Vacuoles, in nerve cells . 

481 

Types of cattle, discussed 


130 

Valves, of veins. 

453 

Types of heads of oats 


390 

of clam shell. 

185 

horses discussed 


126 

of stomach. 

408 

pigs discussed 


133 

Vapor, a form of water . . . 

10 

sheep discussed . 


132 

Variation. 

526 

Typhoid fever, a bacterial 

dis- 


Variations, in beaks of birds 

109 

ease. 


489 

in legs of birds. 

108 

spread by carriers . . 


500 

Varied diet of man .... 

411 

Typhus fever .... 


514 

Variety of animal life .... 

17 

Typical fern, pteris . . 


333 

Varnish, source of. 

352 




Vascular bundles, arrangement 


u 



of. 

267 




formation of tubes by . 

266 

Ulmus americana . . 


10 

of root (conducting vessels) . 

248 

Umbel. 


213 

of woody stems. 

267 



































INDEX 39 

References are to pages 


Vascular system in plants 268 

Vase-like leaves of pitcher plant 366 
Vaseline, use of, in transpira¬ 
tion experiment .... 284 

Vase-shaped organs (arche- 

gonia) of moss .... 329 

Vedalia, beneficial beetle . . 34 

Vegetable nitrogen, source of . 257 

Vegetable oyster, biennial root 252 

food of man.245 

Veins, compared with fibro- 

vascular bundles .... 267 

of leaf.276 

of man .453 

Velamens. 253, 373 

Venation.276 

Veneer.352 

Ventilation.447 

Ventral blood vessel of earth¬ 
worm ..182 

Ventral nerve chaiA of crayfish . 64 

Ventral surface of earthworm 179 
Ventricle (fourth) of brain . 89 

Ventricles of heart. 452 

Venus mercenaria, edible mol- 

lusk.192 

Venus’s flytrap.289 

rapid movement of ... 367 

use of leaves in. 367 

Vermiform appendix .... 408 

Vermin. 514 

Vertebrates, a group of animals . 9 

discussed. 68 

Vetch, member of pulse family 299 

Viability. .223 

Villi, described.414 

Violet, capsule of.238 

cleistogamous flower of . . 204 

example of irregular flower . 204 

Virgin forest in United States . 348 

Virus in inoculation . . . 511 

Viscera, defined.188 

Visceral ganglion of clam 188 

Vitamines. 245, 415 

Vitreous humor . 473 

Vocal cords, location of . . . 445 

Voice box, the . 445 

Voluntary muscle cells 437 

Voluntary muscles . . . 436-437 

Volvox, described.153 

Vomiting . 408 


Vultures, beneficial birds . . 116 

example of Raptores . . . Ill 

W 

Walking sticks.29 

Walnut, family discussed . . 297 

plant protein in. 222 

tree.351 

Walrus. 134 

War gardens.424 

Warm-blooded animals . . . 451 

Warm milk, multiplication of 

bacteria in.316 

Warmth, a condition of the 

growth of bacteria . . . 311 

Washing away of soil by floods 351 
Wasp fly, beneficial insect . . 54 

Wasps, members of Hymenop- 

tera. 45 

Waste materials of photosyn¬ 
thesis (by-products) . . . 279 

Waste products of body . . . 457 

removed by excretion . . . 457 

Water, a necessary condition for 

growth of, bacteria . . . 311 

basis of classifying plants in 

societies.369 

contains bacteria . . . . 310 

composition of. 12 

sanitary measures for protect¬ 
ing .498 

supply, student report on . 499 

Water beetles, destroyers of 

mosquitoes.55 

Waterlilies, air supply of . 370 

structure of stem of ... 370 

Water roots.251 

Water snail, host of liver fluke . 176 

Water supply.462 

Wax, in ear.476 

produced in U. S., value of . 49 

Weasels, destroyed by hawks . 115 

harmful animals.137 

Webbed toes, of swimming 

birds . .. 108 

Wedding flight of bee ... 48 

Weeds, common, list of . . . 301 

definition of.302 

in plant succession .... 375 

reasons for success of . 302 

seeds destroyed by birds . . 117 





































40 


INDEX 


References are to pages 


Wells, as source of water supply 463 
Wheat, a monocotyledon . . 227 

amount produced by U- S. . 296 

member of grass family . . 295 

one of first cultivated plants . 296 

Where bacteria are found . . 310 

Where foodstuffs are stored in 

seeds.229 

White blood corpuscles . . . 450 

White-breasted nuthatch at 

feeding station . . . . 118 

Whitefish, example of a bony 

fish.71 

White grubs, eaten by birds . 35 

parasite.460 

White oak, uses of.352 

White of the eye.473 

White pine, value of ... . 352 

Whiting, edible fish. 80 

Whooping cough, a bacterial 

disease.489 

Wigglers, larvae of mosquitoes . 28 

Wild plants, improvement of, by 

man. 22 

Wiley, Dr. H. W., quoted . . 506 

Willow tree, source of charcoal . 351 

Wind-breaks.348 

Wind-distributed fruits 241 

Window-growing plants, re¬ 
sponse to light in ... 291 

Windpipe.444 

Wind-pollinated flowers, of 

grass family.295 

characteristics of . . . . 210 

Wind pollination.210 

Winglike air sacs of pine pollen 344 

Wing of pine seed.344 

Wings, of birds.107 

of seeds.241 

Winter visitants, examples of . 112 

Wisteria, member of the pulse 

family.299 

Witch-hazel, explosive fruit of 

238, 241 

Wood alcohol.352 

Wood, example of organic mat¬ 
ter . 10 

formation of ... . 265, 341 

Wood borers.34 

Wooded area, under govern¬ 
ment control.361 


Woodpeckers, at suet station . 118 

(downy) permanent residents 111 

food of.42 

Wood-pulp, source of ... 346 

Woody stem, structure of . . 265 

use of elements in . . . . 267 

Woody twig, buds of ... 264 

Wool, source of.132 

indirect product of plants . 376 

Woolly aphis, member of He- 

miptera.32 

Work of the vascular bundle 268 
Work of the yeast plant . . . 321 

of a leaf.274 

of forest ranger.358 

Workers (bees).46 

Worm, planarian.175 

Worm group, discussed . . . 175 

summary of.184 

Worm-like animals, classified . 9 

Worms, classified. 9 

Wren, a useful bird . . . 115 

food of. 42, 115 

X 

Xerophytes.370 

Xylem, conductor of water . . 269 

in fibro vascular bundle of 

corn.266 

in vascular bundle .... 267 

relation to cambium . . . 267 

Y 

Yarrow, divided leaves of . . 278 

Year’s growth of twig, how told 266 
Yeast, in bread making . . . 321 

plant, described.321 

enzyme of.321 

use of.321 

reproduction of.322 

Yellow fever, carried by mos¬ 
quito .494 

caused by protozoa .... 489 

Yellow pine, value of ... 352 

Yolk, of fish eggs.78 

Youth, a period of life . . . 402 

Z 

Zygospore, advantages of . . 307 

of spirogyra.307 

Zymase, work of.427 













































- 











•* 













































































































■ 













































































, 









































































































































/ 

































